Continuity mistake: After Amanda calls Angelica to tell her that she can't make it to her party, she takes her RSVP card from the "Yes" box to the "No" box. The problem is, the check mark on the card magically changes from being by the yes to being by the no without anyone touching it.
Continuity mistake: Right after Amanda changed her mind about going to Angelica's party, there are still at least 5 more cards in her "Yes" box. However, when the shot changes, the "Yes" box is completely empty.