Here’s a little idea I had while browsing over the TV Tropes wiki: Idiot ball.
So you have a game with a bunch of PCs who all want different things. Sitcoms or cartoons or the like give you a host of characters who are sometimes in conflict but sometimes working together toward some other goal.
But there’s always at least one person acting like an idiot. That’s where the situation comedy comes from, right? As Hank Azaria said “Who’s carrying the idiot ball this week?”
Everyone has a PC. Define what thing you want from someone else. They describe why you can’t have it.
Also define for your PC an example of how or why they might act like an idiot. “Doesn’t understand modern machinery” “Always acts like an idiot around pretty girls” “Always showing off for his drunk buddies”, whatever.
Somebody starts with a card that says “The Idiot Ball” on it. While a player holds the Idiot Ball card, anyone can describe their PC doing something boneheadedly stupid. Misunderstanding simple instructions. Leaving your demon possessed brother unattended in a motel room. Getting lost despite the fact that you just spent hours building a detailed map of the cave complex using robot drones. Petting the hideous space monster that is clearly trying to avoid contact with you. You know, the sorts of dumb things characters do in movies and TV all the time.
When they describe your character doing something dumb, they then take the card from you. Now they’re carrying the idiot ball, and anybody can screw over their character, just the same as that guy just did to your character.
For largeish groups (5+?) add a second idiot ball. Or start juggling more balls, each themed at a different sort of flaw: the Disadvantaged Ball (whoever holds this can automatically loses any fights or conflicts they get involved in), the Coward Ball, the Insanity Ball, the Treason Ball (for Paranoia and other games about suspicion) or the Suspect Ball (for murder mysteries).