Bodyswap scenarios could be so much funnier if the people who switched are weird about it
Through some kind of supernatural shinanigans, Dean's soul leaves his body, and in a desperate attempt to keep him earthbound, Cas creates a vacuum in his vessel to suck up Dean's soul. And in order to preserve Dean's body, Cas possesses it with Sam's consent
First thing that happens? The obligatory argument of Dean (In Cas' vessel) yelling at his brother for giving his body to Cas. All while Sam argues Dean did the same thing with the whole Ezikeal situation
Second is Cas (in Dean's body), gets up and tries to approach them to calm things down, only to immediately fall flat on his face because he doesn't know how to walk with bowlegs
Fast forward to them trying to figure out how to switch back, Dean making various pop culture references along the way
They're doing research in the library and Sam has to just speak up
"okay, this is so much weirder seeing Cas do it"
Cas, who's just reading "What have I done?"
"no, not you Cas. Dean- in your body- okay That's - I didn't like saying that"
"the hell you talking about, Sammy?"
Sam grimaces "you doing the whole... Thing"
And in Sam's POV, it's just him watching "Cas" lick his lips while eye fucking "Dean" who's been frowning and squinting, giving off very "I'm gonna kill you" aura at his book
Sam walks in on "Dean" saying Castiel's full name in the mirror, in different tones, and then looking all giddy about it
Sam having to bear witness to "Cas" walking around is various costumes and saying insane nonsense as he parades around
Both Cas and Dean forgetting they're in each other's bodies and getting startled by each other
Dean gets kinda pissy that he's the shortest now, and Cas having to remind him that Jimmy is 6 feet tall
Dean going "You better not take a peek at the goods, Cas"
And Cas giving him the most inscrutable look "Dean, I rebuilt you atom by atom. It's nothing I haven't seen before"
"oh yeah well how would you like it if I looked at your package?"
Sam sitting across from them at a diner "I don't like where this conversation is going"
Hard cut to them at the bunker and Sam and Cas hearing "Dude you got the whole damn rainforest down here!" From the bathroom