Continuity mistake: As Kirby is showing Roz his prom pictures, she sees the picture with his hand on her behind. In the scene her hair on her right changes position in the following shots from on her chest, to slightly behind her shoulder, to completely behind her shoulder.
Continuity mistake: As Marty says "Claire says", he is holding his sandwich is both hands. As Daphne turns towards him and says "shut up", he is holding the sandwich in his left hand and his right hand is on the arm of his chair. There was no time for the switch.