the episode where Cartman locks Butters in the fallout shelter because Kyle chose him instead of Eric to go to Casa Bonita.
the episode where Cartman fools Butters into thinking he's a robot... had Eric sticking suppositories in his ass and singing the "Robot Friend" song.
the episode where Cartman thinks he's dead and only Butters can see him.
the episode where Stan puts together a dance group to compete against the kids from Orange County in a "You Got Served" spoof and Butters' tap-dancing massacre flashbacks.
there's so many more episodes featuring Butters that has me
especially when he breaks out in song singing "If You Leave Me Now" by Chicago.