Continuity mistake: When Felipe is telling Jill that he loves her, the level of their heads changes every shot.
Continuity mistake: At the Thanksgiving dinner scene Jill is explaining her and Jack's secret language, and says that clappa means left. However at the end of the movie during the New Year's scene Monica is approaching her with a bottle from the right side and Jack says "Pokey clappa", at which Jill throws up her right arm to knock out Monica.
Factual error: Jack and Jill claim to be identical twins, but it is impossible for a male and female to be identical twins. They must be fraternal.