The Phoenix Saga (3): Cry of the Banshee - S3-E5
Revealing mistake: When Professor X is telling Juggernaut that he is in his mind, if you look closely you can see there is a disembodied mouth on the right side of Professor X's face that is synchronized with his dialogue. Apparently an animation error. Note: this error may only apply to the DVD version of the episode, as it does not occur on the version of the episode that appears on Disney+. (00:04:00)