After a football is thrown at Richard and Greg in the cafeteria, Dominique Swain's stand-in's face is visible instead of her own.
While Andrea is dancing during The Badheads/Thriftstore Apocalypse first song, Cybil's lips don't match up with the vocals she is supposedly singing.
Dark shape briefly appears in doorway to Andrea's bedroom when Todd is sneaking out of her window. (only visible in widescreen)