Beware Wolf - S2-E2
Continuity mistake: Justin messes his hair up (spiky and brushed back) after dunking his head in the potion, but in the next shot his hair is all flat and down again.
Baby Cupid - S2-E10
Revealing mistake: In the episode where Alex has to look after Cupid by disguising him as a baby, her teacher takes the shaver off Cupid and spins round and shoves it in his pocket. However you can see he's just holding it by his side.
Wizards vs. Vampires on Waverly Place - S2-E26
Deliberate mistake: Justin tells his dad he will write the idea on the white board (the theme in the restaurant/add more of an experience) yet he just scribbles, and in the scenes where you see a bit behind him, the whiteboard has scribbles instead of words where he was supposed to write.
Wizards vs. Vampires on Waverly Place - S2-E26
Continuity mistake: After Justin and Juliet come back from the movie, they sit down in front of the sub station. When Justin and Juliet talk, look at Juliet's left shoulder; her sweater goes from being on her shoulder to slightly off her shoulder every time the camera pans back and forth on them.
Continuity mistake: As Justin comes hysterically in to the restaurant from the lair, he runs over by the door to pull the shades down. A few seconds later when the camera is on Alex, you can see one of the shades is on the ground, However, after Alex says "you turned in your girlfriend to the Monster Hunter council" and Justin is shown, you can see that the shade has been put back in place.
Plot hole: When Justin and Juliet were trapped behind the glass and Juliet let herself be captured by the mummy, so she doesn't burn to ashes when the morning comes, why didn't Juliet just escape? The mummy gave her enough time to turn around and share a moment with Justin, she could've used that time to fight him off, break Justin out and escape. The mummy wasn't very strong and Alex would've shown up 20 seconds later anyway, there wasn't any real reason for Juliet to just let herself be taken away.
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.
The Good, the Bad, and the Alex - S3-E15
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.
Rock Around the Clock - S4-E25
Continuity mistake: In episode 25 of season 4, Harper mentions still being in school and even goes to school during the 50's episode to keep her "perfect attendance." But a few episodes earlier, her and Alex both graduate, and even have an apartment. The episodes seem out of order.
Suggested correction: Yes, episode 25 "Rock Around the Clock" was the 14th episode produced (production code 414) and occurred before they graduated the 17th episode "Wizards vs. Asteroid" (production code 418). This isn't a TV mistake since it was produced in order.