When Alex and Harper are standing outside Alex's locker discussing the 10 minute sale and Gigi, at first Alex is holding some books, then on a shot from behind Alex she puts the books in her locker. Then there is a shot from behind Harper and Alex is telling Harper about saying Gigi's name backwards, then there is a shot from behind Alex again and Alex is suddenly holding the books again, and in the next shot from behind Harper Alex is putting the books back in her locker again.
While Gigi and her wannabes are coming down the stairs, there is a fan being blown at them. This makes all 3's hair blow with the wind, yet when the fan stops and they walk up to Alex and Harper all 3's hair are perfect, without having time to brush their hair.
When we first get introduced to Gigi and her back round girls, they walk down the school stairs. As a joke in the back round you see a boy that is operating the fan. However, if the girls are walking away from the fan, then their hair should be flying forwards, not backwards and fancy like in a shampoo commercial.
Alex and Harper say that Gigi's name spelled backwards is Gigi, but it is really Igig.