So I've thought about the PC's backgrounds for a long time. Here's a list of the ones I think they would have (or had).
Jester - Noble/Acolyte (Yeah okay. Acolyte maaaay not work. Mostly because that I haven't heard Jester speak any other language than infernal & of course common. But it could work.) Molly - Charlatan. (Or entertainer. But after the talks machina episode where Tal revealed the Vicious Mockery lines where just bullshit. Litteral whispering gutteral sounds, and said something along the lines of that he is a fraud. That kinda changed my view.) Nott - I have no ******* clue. (Yep. I'm not really sure. She wasn't a criminal, she was a regular halfling. So, if you have a guess then please tell me.) Beau - Criminal (I feel like she kinda revealed that. Saying multible times "because of my criminaaaaal baaaackground". I think the first time she said it was in the sewer system, before or after fighting the phase spider.) Caduceus - Acolyte/Hermit (Probably one of those. I mean, both would fit. It has to be a background with an additional language as he can speak Sylvan.... right?) Fjord - Sailor (I mean, if I'm wrong here I srsly need to check my understanding of the past months events.) Yasha - Far Traveler (There is a picture in the SCAG. With a woman that looks, appearance wise, strikingly similar to Yasha. I think Yasha was inspired by this picture, but also because that is really all that I can think of that matches her. Since she is from Xhorhas. She is after all, prof in perception.) Caleb - Criminal/Spy/one I'm forgetting (There is some talk about Caleb being a spy (mainly by Laura in the tiefling = ***** episode of talks machina). I'm not sure if I think that's true, maaaybe he is but probably not for the same people. Criminal because he did "evil" stuff. Killing his family n' all. I'm pretty sure that you aren't allowed to kill your family in Wildemount. I feel like I'm forgetting a background or two but those two are the only ones I can come up with at the moment. But he doesn't seem to be proficent in deception and not in stealth. Sooo now that I think about, scratch that criminal one.)
Remember this is just my guess. I'm not saying that these are exactly the ones nor that others opinions are wrong. Of course not. I would be happy to hear your ideas, and maybe someone has ideas as to what background Caleb & Nott has! ^^
Fjord - Sailor is confirmed. At the start of the nautical stuff, Travis outright said on Talks Machina that he picked the Sailor background because it was cool for his backstory but "now I actually need to know about ships!!" Plus, before then, I'm pretty sure he actually used the "Ship's Passage" feature. One of the only ones (maybe THE only one) to clearly use a background feature.
Beau - Criminal is also confirmed, I think, from in-game statements early on like you said.
Others, I don't know but those are good guesses. Doing some reverse-engineering from Critrolestats.com (which is incomplete since the players haven't necessarily outright stated all of their relevant skill bonuses).
Caduceus - I'd lean towards Hermit because it is both fitting and I could *really* see Matt and Talesin having an interesting time with the Discovery background feature. Seems more fitting than Acolyte. However, somehow he is proficient in Perception, but that's not part of either background. However, if his cleric choices were the same as what's offered in Background (since both of those aren't "pick x from a list"), he could have then gone with substituting with any skill proficiency. Or Matt allowed him (or others) to have any proficiency. The only backgrounds that appear to offer Perception outright don't really fit (Faction Agent, Far Traveler, Pirate, Sailor). He is *definitely* not a Pirate or Sailor background! :) So Perception is likely a swapped out proficiency.
Caleb - He's a variant human and is proficient in (at least) Arcana, History, Insight, and Investigation. He got 2 of those from Wizard, and 1 from Variant Human. So one of those (and anything else he's proficient in but hasn't come up) is from his background. He also has two unusual languages (Sylvan and Celestial) and only 1 is from being Human. If we go beyond the PHB, in my mind, he is a perfect example of Haunted One, although that would grant one more skill proficiency we don't know about yet, but would allow either of those languages.
Jester - Actually looks like Charlatan! She has proficiency in Disguise Kit, Forgery Kit, Deception, & Sleight of Hand. And CritRoleStats outright lists her background as Charlatan right from Level 2. I was surprised by this because on the one hand, it seems like a bit of an odd choice on the surface, but looking past the label itself as to what it grants, it actually is quite fitting for someone like Jester who is *very much* a trickster cleric. So forgetting the label of "Charlatan" with those connotations and looking only at the meat of the background, it actually makes very good sense.
Molly - Yeah, I'd say Charlatan as well. CritRoleStats also lists that, and I'm pretty sure they don't add anything like that until there's solid evidence. (And I'm not sure if I'm ready even now to go back and re-watch the Molly stuff to check for the signs.)
Nott - All of her skills are Rogue skills, but she does have two extra obviously from her background. I'd say that her background and class, etc. are likely from her Goblin days on, rather than incorporating her earlier life. I'd imagine those days were as an unclassed NPC sort of deal. However, she is proficient with Alchemy Kit - which makes sense given her earlier life. So who knows? (Well, other than Matt & Sam.) I would say Criminal or Urchin would really fit her (Goblin days forward) backstory well, and could work if Matt allowed swapping in the Alchemy Kit proficiency for the doubled up Thieves' Tools. Either way, it's likely something that grants rogueish skills.
Yasha - I don't know either, and it's especially hard with Ashley's absence making Yasha either not around or just kinda drifting into the background. But thematically (as well as that image you mention), I think Far Traveler is a very good guess.
Fjord - Sailor is confirmed. At the start of the nautical stuff, Travis outright said on Talks Machina that he picked the Sailor background because it was cool for his backstory but "now I actually need to know about ships!!" Plus, before then, I'm pretty sure he actually used the "Ship's Passage" feature. One of the only ones (maybe THE only one) to clearly use a background feature.
Beau - Criminal is also confirmed, I think, from in-game statements early on like you said.
Others, I don't know but those are good guesses. Doing some reverse-engineering from Critrolestats.com (which is incomplete since the players haven't necessarily outright stated all of their relevant skill bonuses).
Caduceus - I'd lean towards Hermit because it is both fitting and I could *really* see Matt and Talesin having an interesting time with the Discovery background feature. Seems more fitting than Acolyte. However, somehow he is proficient in Perception, but that's not part of either background. However, if his cleric choices were the same as what's offered in Background (since both of those aren't "pick x from a list"), he could have then gone with substituting with any skill proficiency. Or Matt allowed him (or others) to have any proficiency. The only backgrounds that appear to offer Perception outright don't really fit (Faction Agent, Far Traveler, Pirate, Sailor). He is *definitely* not a Pirate or Sailor background! :) So Perception is likely a swapped out proficiency.
Caleb - He's a variant human and is proficient in (at least) Arcana, History, Insight, and Investigation. He got 2 of those from Wizard, and 1 from Variant Human. So one of those (and anything else he's proficient in but hasn't come up) is from his background. He also has two unusual languages (Sylvan and Celestial) and only 1 is from being Human. If we go beyond the PHB, in my mind, he is a perfect example of Haunted One, although that would grant one more skill proficiency we don't know about yet, but would allow either of those languages.
Jester - Actually looks like Charlatan! She has proficiency in Disguise Kit, Forgery Kit, Deception, & Sleight of Hand. And CritRoleStats outright lists her background as Charlatan right from Level 2. I was surprised by this because on the one hand, it seems like a bit of an odd choice on the surface, but looking past the label itself as to what it grants, it actually is quite fitting for someone like Jester who is *very much* a trickster cleric. So forgetting the label of "Charlatan" with those connotations and looking only at the meat of the background, it actually makes very good sense.
Molly - Yeah, I'd say Charlatan as well. CritRoleStats also lists that, and I'm pretty sure they don't add anything like that until there's solid evidence. (And I'm not sure if I'm ready even now to go back and re-watch the Molly stuff to check for the signs.)
Nott - All of her skills are Rogue skills, but she does have two extra obviously from her background. I'd say that her background and class, etc. are likely from her Goblin days on, rather than incorporating her earlier life. I'd imagine those days were as an unclassed NPC sort of deal. However, she is proficient with Alchemy Kit - which makes sense given her earlier life. So who knows? (Well, other than Matt & Sam.) I would say Criminal or Urchin would really fit her (Goblin days forward) backstory well, and could work if Matt allowed swapping in the Alchemy Kit proficiency for the doubled up Thieves' Tools. Either way, it's likely something that grants rogueish skills.
Yasha - I don't know either, and it's especially hard with Ashley's absence making Yasha either not around or just kinda drifting into the background. But thematically (as well as that image you mention), I think Far Traveler is a very good guess.
Thank you! ^^ The haunted one for Caleb is a VERY good guess. Though I do not have the books and the COS that I think the background comes from is not currently on my list of must have books since my players are pretty new to d&d. I guess criminal could work for Nott. But I'm wondering if what she did together with the Goblins are true. Maybe she said she was working with some goblins after her death but I don't remember it sadly. I though she was on the run since she awoke. I didn't even think about Clerics not being allowed a perception proficiency, which is kindaaaa weird but nvm. Thanks for your input! ^^
Regarding Caleb SPECIFICALLY, I'm running through all possible backgrounds, and what Caleb's proficient in. Thanks to the Skilled feat he got at lvl 12, Caleb's proficient in Intimidation, Perception and Persuasion, so what's left is Arcana, Deception, History, Insight and Investigation. 2 come from the Wizard class, 1 comes from being a Human Variant race, and the other 2 comes from his background. Only Deception cannot be chosen from the Wizard class, but that could be selected as the Human skill, so any background that involve these 5 are viable, but story-wise, will they make sense? In many of these scenarios, I think Deception is selected as the Human trait, fitting since Caleb started teamed up with Nott.
Clan Crafter - Proficient in History and Insight; (Wiz Prof: Arcana & Investigation, Human Prof: Deception) Wizards don't typically "labor under a dwarf master," and Caleb doesn't speak Dwarven, so this seams highly unlikely.
Cloistered Scholar - Proficient in History, and either Arcana (required), Nature or Religion; (Wiz Prof: Insight & Investigation, Human Prof: Deception) His starting equipment is everything he needs to write scrolls and copy spells into his spellbook, and he can select 2 free languages of his choice. This background's Feature is Library Access, which grants him free access to many of the most common of libraries. This seams VERY likely, and this is only the second Background I've stopped at that's viable!
Faction Agent - Proficient in Insight and one Int (Arcana, History or Investigation), Wis or Cha (Deception) skill appropriate to your faction; (You can mix and match proficiencies any way you want.) Like the previous background, you can learn 2 languages of your choice with this one, and Liam can go wild with how to build Caleb since Caleb is proficient in all mentioned skills. The faction in question would of course be homebrew to be the Empire, as he has dreamed of serving the Empire for a long time, but his starting equipment does not contain a badge, emblem or written text regarding the Empire. Very likely, but as I read the background's lore, Caleb would have needed to already be in SERVICE of the Empire, so that's the only dent in this background.
Haunted One - Proficient in 2 between Arcana, Investigation (the 1st 2 are required), Religion or Survival; (Wiz Prof: Insight & History, Human Prof: Deception) Daergiel in the post before mine has several strong points, as Caleb's past is quite traumatizing to him, especially early on, and can explain where he understood Sylvan and Celestial.. This is also VERY likely, but the only problem I have is: What Gothic Trinket did Caleb get? Or did Liam homebrew this part? The Harrowing Events don't connect well with what Caleb did (to my memory at least) either, so it's possible Liam homebrew this as part as well.
Investigator - Proficient in 2 between Insight, Investigation (the 1st 2 are required) or Perception; (Wiz Prof: Arcana & History, Human Prof: Deception) The starting equipment could have very easily have been homebrew, and Caleb isn't proficient in tools, so he could have replaced tool proficiencies with 2 languages, but you can't ignore one of the possible Paths to Mystery: "You survived the destructive use of a magic device that wiped out your home. Members of a secret organization found you. You now work with them, tracking down dangerous supernatural phenomena and preventing them from doing harm." If this doesn't line up 100%, at least Liam likely got inspiration from this Path for his character.
Sage - Proficient in Arcana and History; (Wiz Prof: Insight & Investigation, Human Prof: Deception) The only things from the starting equipment that seam off are a small knife and the letter from a dead colleague. It could have been a burnt spellbook, but one was bought after the adventure started, so that's not likely. However, Caleb could easily be a Researcher or Wizard's apprentice, both inspiration to research and create Caleb's Transmogrification spell, and this is a very go-to background for Wizards.
Urban Bounty Hunter - Proficient in 2 between Deception, Insight (the 1st 2 are required), Persuasion and Stealth; (Wiz/Human Prof: Arcana, History & Investigation) This background has tool proficiencies Caleb is not interested in, so it's likely Liam traded that in for 2 languages instead. This is highly unlikely because the lore of being a bounty hunter doesn't fit Caleb's lore. The only sense I can make of this is since he was teaming with Nott, but that's a bit of a stretch.
Black Fist Double Agent - Proficient in Deception and Insight; (Wiz/Human Prof: Arcana, History, Investigation) This background is from the Curse of Strahd, and seems to fit that particular setting really well, and as far as I'm aware, the Mighty Nein didn't even step foot in that realm., so this is certainly an impossibility.
Mage of High Sorcery - Proficient in Arcana and History; (Wiz Prof: Insight & Investigation, Human Prof: Deception) This feels like a fitting background for a Wizard, except the background's lore can be retconned and replaced with a homebrew. This background would allow Liam to pick between the Lunitari and Solinari Lunar spells. Caleb's wiki states it's unknown why or how Caleb knows 6 cantrips, and this would explain it. Furthermore, the Solinari Lunar spell set allows you to pick Produce Flame, a Druid spell, which can explain how Caleb's reworked this spell into his own Wizard variant of said spell. He also knows 1 Abjuration and 1 Conjuration lvl 1 spell with special restrictions, but if he's a Wizard, he can just copy the spell into his book. Mechanically, this background makes a LOT of sense.
Gambler - Proficient in Deception and Insight; (Wiz/Human Prof: Arcana, History & Investigation) Caleb isn't much of a gambler, and this background comes from Acquisitions Incorporated, and I don't think Critical Role would take their content. This is another impossibility.
Rival Intern - Proficient in History and Investigation; (Wiz Prof: Arcana & Insight, Human Prof: Deception) For similar reasons stated above (because Caleb is no intern, and this also came from Acquisitions Incorporated), this is yet another impossibility.
Izzet Engineer - Proficient in Arcana and Investigation; (Wiz Prof: History & Insight, Human Prof: Deception) Not likely for various reasons, but an interesting pick, even if the lore and mechanics don't line up. Just look at the Izzet Guide Spells. As a Wizard, I'd want to pick a background like this!
And that's all I got. With all that said and done, I think Cloistered Scholar, Haunted One and Mage of High Sorcery are the 3 most likely backgrounds for Caleb. I'm open to corrections if anyone finds any in my post.
So I've thought about the PC's backgrounds for a long time. Here's a list of the ones I think they would have (or had).
Jester - Noble/Acolyte (Yeah okay. Acolyte maaaay not work. Mostly because that I haven't heard Jester speak any other language than infernal & of course common. But it could work.)
Molly - Charlatan. (Or entertainer. But after the talks machina episode where Tal revealed the Vicious Mockery lines where just bullshit. Litteral whispering gutteral sounds, and said something along the lines of that he is a fraud. That kinda changed my view.)
Nott - I have no ******* clue. (Yep. I'm not really sure. She wasn't a criminal, she was a regular halfling. So, if you have a guess then please tell me.)
Beau - Criminal (I feel like she kinda revealed that. Saying multible times "because of my criminaaaaal baaaackground". I think the first time she said it was in the sewer system, before or after fighting the phase spider.)
Caduceus - Acolyte/Hermit (Probably one of those. I mean, both would fit. It has to be a background with an additional language as he can speak Sylvan.... right?)
Fjord - Sailor (I mean, if I'm wrong here I srsly need to check my understanding of the past months events.)
Yasha - Far Traveler (There is a picture in the SCAG. With a woman that looks, appearance wise, strikingly similar to Yasha. I think Yasha was inspired by this picture, but also because that is really all that I can think of that matches her. Since she is from Xhorhas. She is after all, prof in perception.)
Caleb - Criminal/Spy/one I'm forgetting (There is some talk about Caleb being a spy (mainly by Laura in the tiefling = ***** episode of talks machina). I'm not sure if I think that's true, maaaybe he is but probably not for the same people. Criminal because he did "evil" stuff. Killing his family n' all. I'm pretty sure that you aren't allowed to kill your family in Wildemount. I feel like I'm forgetting a background or two but those two are the only ones I can come up with at the moment. But he doesn't seem to be proficent in deception and not in stealth. Sooo now that I think about, scratch that criminal one.)
Remember this is just my guess. I'm not saying that these are exactly the ones nor that others opinions are wrong. Of course not. I would be happy to hear your ideas, and maybe someone has ideas as to what background Caleb & Nott has! ^^
Best the loot & luck to you all! ^^
Fjord - Sailor is confirmed. At the start of the nautical stuff, Travis outright said on Talks Machina that he picked the Sailor background because it was cool for his backstory but "now I actually need to know about ships!!" Plus, before then, I'm pretty sure he actually used the "Ship's Passage" feature. One of the only ones (maybe THE only one) to clearly use a background feature.
Beau - Criminal is also confirmed, I think, from in-game statements early on like you said.
Others, I don't know but those are good guesses. Doing some reverse-engineering from Critrolestats.com (which is incomplete since the players haven't necessarily outright stated all of their relevant skill bonuses).
Caduceus - I'd lean towards Hermit because it is both fitting and I could *really* see Matt and Talesin having an interesting time with the Discovery background feature. Seems more fitting than Acolyte. However, somehow he is proficient in Perception, but that's not part of either background. However, if his cleric choices were the same as what's offered in Background (since both of those aren't "pick x from a list"), he could have then gone with substituting with any skill proficiency. Or Matt allowed him (or others) to have any proficiency. The only backgrounds that appear to offer Perception outright don't really fit (Faction Agent, Far Traveler, Pirate, Sailor). He is *definitely* not a Pirate or Sailor background! :) So Perception is likely a swapped out proficiency.
Caleb - He's a variant human and is proficient in (at least) Arcana, History, Insight, and Investigation. He got 2 of those from Wizard, and 1 from Variant Human. So one of those (and anything else he's proficient in but hasn't come up) is from his background. He also has two unusual languages (Sylvan and Celestial) and only 1 is from being Human. If we go beyond the PHB, in my mind, he is a perfect example of Haunted One, although that would grant one more skill proficiency we don't know about yet, but would allow either of those languages.
Jester - Actually looks like Charlatan! She has proficiency in Disguise Kit, Forgery Kit, Deception, & Sleight of Hand. And CritRoleStats outright lists her background as Charlatan right from Level 2. I was surprised by this because on the one hand, it seems like a bit of an odd choice on the surface, but looking past the label itself as to what it grants, it actually is quite fitting for someone like Jester who is *very much* a trickster cleric. So forgetting the label of "Charlatan" with those connotations and looking only at the meat of the background, it actually makes very good sense.
Molly - Yeah, I'd say Charlatan as well. CritRoleStats also lists that, and I'm pretty sure they don't add anything like that until there's solid evidence. (And I'm not sure if I'm ready even now to go back and re-watch the Molly stuff to check for the signs.)
Nott - All of her skills are Rogue skills, but she does have two extra obviously from her background. I'd say that her background and class, etc. are likely from her Goblin days on, rather than incorporating her earlier life. I'd imagine those days were as an unclassed NPC sort of deal. However, she is proficient with Alchemy Kit - which makes sense given her earlier life. So who knows? (Well, other than Matt & Sam.) I would say Criminal or Urchin would really fit her (Goblin days forward) backstory well, and could work if Matt allowed swapping in the Alchemy Kit proficiency for the doubled up Thieves' Tools. Either way, it's likely something that grants rogueish skills.
Yasha - I don't know either, and it's especially hard with Ashley's absence making Yasha either not around or just kinda drifting into the background. But thematically (as well as that image you mention), I think Far Traveler is a very good guess.
Thank you! ^^ The haunted one for Caleb is a VERY good guess. Though I do not have the books and the COS that I think the background comes from is not currently on my list of must have books since my players are pretty new to d&d. I guess criminal could work for Nott. But I'm wondering if what she did together with the Goblins are true. Maybe she said she was working with some goblins after her death but I don't remember it sadly. I though she was on the run since she awoke. I didn't even think about Clerics not being allowed a perception proficiency, which is kindaaaa weird but nvm. Thanks for your input! ^^
Regarding Caleb SPECIFICALLY, I'm running through all possible backgrounds, and what Caleb's proficient in. Thanks to the Skilled feat he got at lvl 12, Caleb's proficient in Intimidation, Perception and Persuasion, so what's left is Arcana, Deception, History, Insight and Investigation. 2 come from the Wizard class, 1 comes from being a Human Variant race, and the other 2 comes from his background. Only Deception cannot be chosen from the Wizard class, but that could be selected as the Human skill, so any background that involve these 5 are viable, but story-wise, will they make sense? In many of these scenarios, I think Deception is selected as the Human trait, fitting since Caleb started teamed up with Nott.
Clan Crafter - Proficient in History and Insight; (Wiz Prof: Arcana & Investigation, Human Prof: Deception) Wizards don't typically "labor under a dwarf master," and Caleb doesn't speak Dwarven, so this seams highly unlikely.
Cloistered Scholar - Proficient in History, and either Arcana (required), Nature or Religion; (Wiz Prof: Insight & Investigation, Human Prof: Deception) His starting equipment is everything he needs to write scrolls and copy spells into his spellbook, and he can select 2 free languages of his choice. This background's Feature is Library Access, which grants him free access to many of the most common of libraries. This seams VERY likely, and this is only the second Background I've stopped at that's viable!
Faction Agent - Proficient in Insight and one Int (Arcana, History or Investigation), Wis or Cha (Deception) skill appropriate to your faction; (You can mix and match proficiencies any way you want.) Like the previous background, you can learn 2 languages of your choice with this one, and Liam can go wild with how to build Caleb since Caleb is proficient in all mentioned skills. The faction in question would of course be homebrew to be the Empire, as he has dreamed of serving the Empire for a long time, but his starting equipment does not contain a badge, emblem or written text regarding the Empire. Very likely, but as I read the background's lore, Caleb would have needed to already be in SERVICE of the Empire, so that's the only dent in this background.
Haunted One - Proficient in 2 between Arcana, Investigation (the 1st 2 are required), Religion or Survival; (Wiz Prof: Insight & History, Human Prof: Deception) Daergiel in the post before mine has several strong points, as Caleb's past is quite traumatizing to him, especially early on, and can explain where he understood Sylvan and Celestial.. This is also VERY likely, but the only problem I have is: What Gothic Trinket did Caleb get? Or did Liam homebrew this part? The Harrowing Events don't connect well with what Caleb did (to my memory at least) either, so it's possible Liam homebrew this as part as well.
Investigator - Proficient in 2 between Insight, Investigation (the 1st 2 are required) or Perception; (Wiz Prof: Arcana & History, Human Prof: Deception) The starting equipment could have very easily have been homebrew, and Caleb isn't proficient in tools, so he could have replaced tool proficiencies with 2 languages, but you can't ignore one of the possible Paths to Mystery: "You survived the destructive use of a magic device that wiped out your home. Members of a secret organization found you. You now work with them, tracking down dangerous supernatural phenomena and preventing them from doing harm." If this doesn't line up 100%, at least Liam likely got inspiration from this Path for his character.
Sage - Proficient in Arcana and History; (Wiz Prof: Insight & Investigation, Human Prof: Deception) The only things from the starting equipment that seam off are a small knife and the letter from a dead colleague. It could have been a burnt spellbook, but one was bought after the adventure started, so that's not likely. However, Caleb could easily be a Researcher or Wizard's apprentice, both inspiration to research and create Caleb's Transmogrification spell, and this is a very go-to background for Wizards.
Urban Bounty Hunter - Proficient in 2 between Deception, Insight (the 1st 2 are required), Persuasion and Stealth; (Wiz/Human Prof: Arcana, History & Investigation) This background has tool proficiencies Caleb is not interested in, so it's likely Liam traded that in for 2 languages instead. This is highly unlikely because the lore of being a bounty hunter doesn't fit Caleb's lore. The only sense I can make of this is since he was teaming with Nott, but that's a bit of a stretch.
Black Fist Double Agent - Proficient in Deception and Insight; (Wiz/Human Prof: Arcana, History, Investigation) This background is from the Curse of Strahd, and seems to fit that particular setting really well, and as far as I'm aware, the Mighty Nein didn't even step foot in that realm., so this is certainly an impossibility.
Mage of High Sorcery - Proficient in Arcana and History; (Wiz Prof: Insight & Investigation, Human Prof: Deception) This feels like a fitting background for a Wizard, except the background's lore can be retconned and replaced with a homebrew. This background would allow Liam to pick between the Lunitari and Solinari Lunar spells. Caleb's wiki states it's unknown why or how Caleb knows 6 cantrips, and this would explain it. Furthermore, the Solinari Lunar spell set allows you to pick Produce Flame, a Druid spell, which can explain how Caleb's reworked this spell into his own Wizard variant of said spell. He also knows 1 Abjuration and 1 Conjuration lvl 1 spell with special restrictions, but if he's a Wizard, he can just copy the spell into his book. Mechanically, this background makes a LOT of sense.
Gambler - Proficient in Deception and Insight; (Wiz/Human Prof: Arcana, History & Investigation) Caleb isn't much of a gambler, and this background comes from Acquisitions Incorporated, and I don't think Critical Role would take their content. This is another impossibility.
Rival Intern - Proficient in History and Investigation; (Wiz Prof: Arcana & Insight, Human Prof: Deception) For similar reasons stated above (because Caleb is no intern, and this also came from Acquisitions Incorporated), this is yet another impossibility.
Izzet Engineer - Proficient in Arcana and Investigation; (Wiz Prof: History & Insight, Human Prof: Deception) Not likely for various reasons, but an interesting pick, even if the lore and mechanics don't line up. Just look at the Izzet Guide Spells. As a Wizard, I'd want to pick a background like this!
And that's all I got. With all that said and done, I think Cloistered Scholar, Haunted One and Mage of High Sorcery are the 3 most likely backgrounds for Caleb. I'm open to corrections if anyone finds any in my post.
I'll pop this into a spoiler for anyone not through watching campaign 2...
Critrolestats.com has all the character sheets, based on that the backgrounds were:
Beau: Criminal (Spy), Caduceus: Far Traveller, Caleb: Haunted one, Fjord: Sailor, Jester: Charlatan, Nott/Veth: Guild Artisan, Yasha: Haunted One, Mollymauk: Charlatan.
ooooohhhhh thanks for this!