Continuity mistake: In the episode "First Kiss," Justin has a girlfriend, Miranda. But in this episode Justin starts dating this new girl from his class, who's actually the same Miranda. This doesn't make any sense. How is she a new student and how could they just meet if they were dating eight episodes ago?
Continuity mistake: After Mrs. Russo puts Justin and Max in the lair, she is wondering if she should put the big lock on the door or not. She decides not to and puts the lock down on the counter. Two shots later you see the lock is back on the door, but unlocked. You never see Mrs. Russo put the lock on the door.
Continuity mistake: When Alex, Justin and Harper find Stevie's brother, he tells them Stevie left the hall of transfers before he could become a full wizard. In season 4 when Alex and Justin become full wizards, they do not go to the hall of tranfers but are given full powers by the headmaster.
Continuity mistake: Alex's hair in season 3 changes back and forth between her shoulder length Bob and her long curly hair. The first instance of this is in the first episode with Mason in it. She had short hair in the previous episode, then it's long and curly in this episode, and then the following episode it's short again. This happens many times in season 3.
Continuity mistake: In the episode with Alex at the art museum and Justin a teacher's assistant, as Alex is in the room with all the paintings, she puts a piece of rope around the door handles. Later on when Alex says, "Go ahead scream panic," we see Alex in front of the door, but the rope is gone, but the next time it shows Alex the rope is there again.
Continuity mistake: When Alex spills a little chocolate, there should be a small puddle at her feet. But in the next shot, there is chocolate stretching right to the other side of the room. There is no way that the chocolate could have spread that far.
Continuity mistake: When Harper makes all the apples fall down, there is one more left on the stand. When it switches to Alex and then switches back to the stand, there are no apples on it. In the next shot the one single apple has reappeared back on the stand, then disappears again in the next shot.
Continuity mistake: In the mummy episode, Juliet states that sunlight kills her. However, in the episode before that (Three Monsters), she is shown walking into the sub shop with a calzone box during the day.