there are a few pokemon that have big grins but i have been thinking about gastly since the grin came up in that thread: there was a gastly balloon in the first part of that investigation with atsushi, hsy found another prankster gastly in the hospital, it's purple, it's a gaseous pokemon so there wouldn't be anything for sagi to hit when he yeeted himself, gastly learns hypnosis naturally at a low level which would cause people to fall asleep, its pokedex entries suggest that it can also just make people faint if they're inside its body...

the main problem is i'm not sure how much of this counts as out of game pokemon knowledge and therefore how much counts as circumstantial :|a