Headcanon that Pim is an extreme horror fan, y'know, the kind of horror that become infamous on the Internet? Movies like: August Underground,Hostel,The guinea pig collection, THOSE kinds of movies.
Imagine when it's his turn to do movie night and they're finishing Cannibal Holocaust and Pim turns to Charlie like,"Wow! Wasn't that great Charlie! :D" meanwhile Charlie's sitting there wide eyed, pale as a ghost, gripping his chest like,"Pim what the FUCK "
I just really like "the bright and happy character has this one edgy trait" trope and I will not apologize for that