“We were going through the Men of Letters bunker, after the Winchesters had disappeared, looking for clues to find the cure for Croatoan B. Much happened there, including our friend and the leader of our expedition, Lee Brockway, getting attacked by djinn. He was understandably shaken up by this.
“Well, I was exhausted after counter-warding the entire place so that our demons -- Meg and Crowley -- could walk without trapping themselves every two steps, so Crowley put me to bed, then headed to the kitchen where Lee was brooding pensively.”
There was a beat there and Castiel was clearly wrestling with his composure; apparently, the seraph found this to be hilarious even years after the event itself.
“I woke up without my demon, so I decided to go find him. I overheard him and Lee talking in the kitchen, but I wasn’t paying much attention to the conversation itself. I just made myself invisible and crawled under the table, meaning to perhaps tease Crowley. Right as he and Lee were having a, ah-- ‘feelsy’ moment, and Lee said, ‘Thanks, I mean it,’ I-- stuck my nose in Crowley’s crotch.”
Cue a good two minutes of Castiel laughing himself absolutely silly.
Seriously. A seraph laughing until his face ached.
And he was still trying his hardest not to outright giggle as he went on, “Crowley and Lee both weren’t aware I was there. Crowley shoved backwards and asked Lee what he thought he was doing. And I could not stop myself laughing there; Lee was mildly homophobic, and the idea of Lee coming onto Crowley, and Crowley thinking it was Lee--”
Nope. There Cas was off again, this time bracing his ribs and just laughing to the point of tears at the memory. Hopefully Alice would forgive this adjacent version of Castiel his humor.
It was the best prank he never intended to play.