basically I changed the rule because this way it allows for people to put memes in their games. Had a few games last time with rickrolls and cutout characters of real polititians. You don't HAVE to use preexisting assets you don't own, the rule is just there to let people do whatever, as long as the game is bad.
yeah fair use is a good starting point. If your game looks like a parody (and it should, given that you're making bad games for this jam) then it definitely can't be mistaken with the original content. However, fair use is not the end to all creation means, and the definition is kind of blurry anyway. If a big company wants to DMCA you for using their content, they will and it's their right.