Quote from CheesyLeviathan >>

It was my first ever game of D&D and we were all in 6th or 7th grade (and also new), so keep in mind the game was very ridiculous.

We’re in a dungeon for a reason I’ve long since forgotten. There’s a hallway ahead of us, and the rogue successfully identifies traps.

The fighter cautiously steps forward. Scythes fly out of the wall and he is killed by 12d20 slashing damage.

I ask the DM if I can make a perception check to find “boots of trap immunity”, something I made up on the spot. Because I am in sixth grade at the time, I am smelling for them.

I roll a natural 20, and the DM says I’ve been wearing said boots this entire time. So I crossed the hall while everyone else tried to make their dex saves.

 This is real new-inexperienced-child-group gameplay and I love it

Truly outstanding,  thank you for sharing!

We were exploring a dungeon and our insane murderhobo warlock was scouting for us ( because she was the only one insane enough to do it ) and she found a giant purple glowing glass orb standing in the middle of a foul smelling pool of some unidentifiable liquid. There were also strange skeletons with mutalated jaws scattered in the room. The warlock decides to drink from the pool because she was bored. The dm describes a strange solid lump slithering down her throat and she falls unconcious. My ranger and the rest of the party come down and find her unconcious and I realize mindflayer involvement. We guessed that she had drunk from the pool (she had a bad habit of drinking any liquid we came across) and that a mindflayer tadpole had gotten into her brain. Our monk said we should try brain surgery, and since we knew she would die no matter what, we decided to try. I had the highest medicine proficiency so I rolled and got a nat 20. Instantly cut open her head with a shortsword and took out the tadpole. Of course the first thing she did when she woke up was shatter the globe, causing an angry elder brain and neothelid to attack our party of four level three characters. 

Quote from The_Summoning_Dark >>

We were exploring a dungeon and our insane murderhobo warlock was scouting for us ( because she was the only one insane enough to do it ) and she found a giant purple glowing glass orb standing in the middle of a foul smelling pool of some unidentifiable liquid. There were also strange skeletons with mutalated jaws scattered in the room. The warlock decides to drink from the pool because she was bored. The dm describes a strange solid lump slithering down her throat and she falls unconcious. My ranger and the rest of the party come down and find her unconcious and I realize mindflayer involvement. We guessed that she had drunk from the pool (she had a bad habit of drinking any liquid we came across) and that a mindflayer tadpole had gotten into her brain. Our monk said we should try brain surgery, and since we knew she would die no matter what, we decided to try. I had the highest medicine proficiency so I rolled and got a nat 20. Instantly cut open her head with a shortsword and took out the tadpole. Of course the first thing she did when she woke up was shatter the globe, causing an angry elder brain and neothelid to attack our party of four level three characters. 

 Still, that's a cool save. 

I play as a Bard/Fighter multiclass. While in town, I decided to woo one of the most beautiful townsfolk, and successfully asked her on a date. 

Problem was, the other PC's decided to prank me, which led to one of our PC's going too far and poisoning my food with a powerful paralysis poison. I failed the save, had to get greater restorationed, and the date was going rocky. I gave a speach to the the NPC, and declared her the "finest jewel my eyes ever did wrought" among other things. The DM asked me to roll a Performance check to see if the speech had successfully saved the night, and I managed a fabulous nat 20. Afterward I managed to woo her all the way to my chambers, where to everyone's surprise I managed another nat 20 on my next performance check. 

The bard was excessively happy that evening, as was the person playing him. 

We were playing a homebrew campaign and not me, but one of my friends was playing a barbarian and asked if he could attempt to remove the two dead ogres' male genitalia. The DM was amused by this and asked him to role a medicine check to successfully amputate the parts. He rolled a nat 20 on one ogre and a 19 on the other. The DM puts his hand on his head and says "what the F' are you going to do with two ogre sacs?" We all burst out laughing and it took a few minutes for us to get back on track. Possibly the funniest moment in our campaign.

So, I was a level six druid in AL and we had to save this poor kid from two demons so I kinda summoned eight panthers to kill everything-

two of my panthers were harassing one of the demons, which exploded in a fit of rage and I made the saving throws for them (one did a nat 20 and got 23, the other 19 and got 22)

So when one of my members by the demon got hit (failed the save) it did eight damage... the exact number of hit points my panthers had (they got a little beat up)

I said, "wow that would have killed them!"

to which the DM replies "That's what I'm trying to do!"

This ones Kinda Stupid.

We were on a Chinook, with people who were not who they said they were.

I say that I'm gonna stealth Stab one of them in the back of the head

DM "Roll for stealth and Roll to hit"

Both Nat 20's 

I ended up smashing his skull to dust with one blow of a dagger

Story 2

We were on our way to a dwarven ruin, where 2 dwarf researchers resided. 

DM "Roll for Perception"

I roll a 20

my friend rolls a 1

I pull my friend out of a way from a Giant Crossbow bolt.

I gave my players a Luck Charm. Every 2 sessions they can roll a nat 20 once. They never it used in combat which I love.

The situation is this: The players are in court against Derth Frensworn, the prince of the Frensworn empire. They’re one defense after being put to trail for killing the princess. The lawyer they had was a coward and didn’t really even speak out. They used the luck charm to give him enough balls to stand up. And guess what? They got launched out a canon a session later because the lawyer was a criminal. 

Doesn’t sound funny until you saw their face and what the gnome barbarian said “I WASTED THAT ON A ***** CRIMINAL!?” Who later went on to become a criminal.

This was a strange one, to say the least.

I played a Paladin starting at level 5. We started our campaign by fighting a bunch of frogs for a few pieces of gold to pay off debt. I had decided to climb a tree but failed multiple times. At some point, it became 2 rolls: One for athletics to climb the tree and an attack roll for a bird that pecked me off once. 

After succeeding the climb roll:

DM: "The bird rolls to attack because you're close to the nest."

Me, thinking the bird probably has no chance of hitting me given my 18 AC: "Alright."

DM: goes silent

Me: "...god damn it."

DM: "The bird just divebombs onto you and causes you to take 10 points of falling and piercing."

I started that fight with roughly 39 health.

I finished with 13 because of that stupid bird

I was DMing and my players came upon a forest of ghouls. One of my players (playing Link) asked if he could see the Master Sword. He got a Nat 20 and so I made up on the spot that somehow they were transported to the Korok forest in Hyrule (Hyrule was already a continent in the world) and the ghouls had been eating Koroks. The players engage in battle. The player who was playing Link also was playing Zelda and he had her fly up 120ft into the air since she was at low HP. I had a Ghoul attempt to attack her and rolled the dice out for all the players to see. It was a Nat 20, this happened twice in a row.

"Soooo the ghoul jumps 120ft into the air and bites Zelda's ankle."

We all burst out laughing and still joke about it to this day.