I shoot the railgun out of the BBEG’s hands, and then show him that I can blow up more than just castles, by blowing him into pieces with my railgun.

you just sat on an old chair, and then it collapsed under your weight, making you fall off a cliff to your (likely) Doom.

Well according to the "The Zarnecki Incursion" episode of Big Bang Theory  "your doom" is synonymous with 4 nerds with a Bat'Leth replica so I'll be fine. (Unless they bring Penny too...)

You're having a nice day visiting Los Angeles when suddenly there's a real-life Sharknado. 

I wild shape into a Shark  Pufferfish and go for a swim. If the sharks eat me it's there loss

Your sucked into a fairy-tail and are slowly being boiled by three little pigs 

I roll an athletics check, get a nat 20, jump out of the pot, throw the pigs into the pot, and then after they're done make pork sandwiches for dinner.

You are about to be thrust into the iron maiden.

I grab a lute and start jamming with the band. They acceot me as one of theur own and we do a world tour together.

You are in an acid tank with an acid-immune shark.

I wild shape into an Acid-immune Pufferfish

You go into a portal which takes you into another portal, and then that portal takes you back to the first portal. you are now stuck in this never ending loop. whilst in this loop you can't cast spells, use racial or class ability's, and you have no friends. Your beginning to feel sick and might puke your guts out at any second...

I use misty step from the fey touched feat, and teleport out. I then throw stuff into the looping portals so that nobody else will get stuck.

A giant just smashed you with a table like a giant fly swatter

Haha! I am also a giant so that does not do a thing. 

I run away from the black hole that sucked up the scenario you made

You were on a swing set and you accidentally swung hard enough to go upside down

Ok I can start us back up:

You realized your boyfriend/girlfriend/other was a demon and was hunting you down.

I am Joe Bob the Slayer of All.

You're trapped in an unbreakable, indestructible cage that has blocked teleportation nd planar trval, and you have no air.

Quote from E_L_L_I_O_T_T >>

I am Joe Bob the Slayer of All.

You're trapped in an unbreakable, indestructible cage that has blocked teleportation nd planar trval, and you have no air.

 Because I am the cage. (ik a bad answer lol)

You just got stabbed my a polymorphed dragon and you are now on the verge of death

Luckily I'm a druid in wild shape so dropping to zero just means I return to my normal form. 

After a  long and hard fight you've been worn down in HP. You're low on spells. You've used up you special abilities. But it's worth it because you're about to the strike the final blow against the BBEG.. OH WAIT! The BBEG polymorphs and reveals himself to actually be Shaggy, who up until now had only been using 0.003% of his power.

I jump into my portable hole, and live the rest of my days inside it, never to be seen again.

You go into a New portal which hasn't been blocked up, which takes you into another portal, and then that portal takes you back to the first portal. you are now stuck in this never ending loop. whilst in this loop you can't cast spells, use racial, class or feat ability's, you have no magic Items and you have no friends. Your beginning to feel sick and might puke your guts out at any second...

I just stop moving forward...

You are stuck in a maze with no exit, and it is in an antimagic field. It has a ceiling...

I use my holy avenger to smash through the roof, and then pull out my spell-storing ring and cast dimension door

Your not falling down a cliff, and this time your not falling up or across a cliff either, you falling Through a cliff

But it is impossible to fall through a cliff, so it is a dream!

You are in a portable hole and it has been closed and magically locked, you will soon start suffocating. You are a level one barbarian with an intelligence of 4, and you have no allies and friends.

I am an Air Genasi and need not breathe.

You are a beginning first-level adventurer journeying down the road when suddenly four goblins get a surprise round on you to unload their arrows. 

Quote from Lorien_Alderon >>

But it is impossible to fall through a cliff, so it is a dream!

You are in a portable hole and it has been closed and magically locked, you will soon start suffocating. You are a level one barbarian with an intelligence of 4, and you have no allies and friends.

 Nothing is impossible