Continuity mistake: When Debra is making the buttons, they focus on her making one, and you can see the stupid one already in the basket. Then they focus on her making the same stupid button next, when it was already in the basket before.
Continuity mistake: When they are preparing for the concert, the girls are setting up stuff on both sides of the entrance door (inside and outside). In all shots, the credit card stickers are in the same place, in the left corner of the right door, whereas they should switch sides for the inside and outside shots. It's most noticeable because of the huge Amex sticker on the right.
Continuity mistake: When everyone is waiting for the police to come and arrest Warren he keeps losing and re-finding his jacket. Mark, Lucas, and Warren are all dancing for everyone on the couch. In each shot that switches between the trio and the people on the couch, Warren's jacket is on and the off and then on again.
Continuity mistake: When Eddie is examining Mark's CD, he takes his magnifying glasses off. They pan to a shot of the back of his head where he takes them off again.