Other mistake: In a previous episode, it says that Phoebe and Max's ice breath can't touch or it'll freeze the whole city. In this episode they blow their ice breath at each other twice.
Welcome to the Family Part 2 - S2-E25
Other mistake: Throughout this episode, Max is captured by villains and is about to be bitten by a vat of hermit crabs. It's pretty obvious that between every scene of Max, instead of the platform lowering, it's just getting higher. Clearly, Max should've got to the hermit crabs about halfway through the episode.
Are You Afraid of the Park? - S3-E5
Other mistake: When Nora lasers Phoebe her clothes have holes in them but Nora lasers Billy all the time and his clothes are fine.
Thunder Van - S2-E1
Other mistake: The Thunder Van is claimed to be soundproof, but when Hank finished pranking the kids, Phoebe could be heard talking to Barb from inside it.
Other mistake: Even though Max nor Phoebe control the whip, just the fact they are "supes" should have allowed them to control it.