Vampire Bats and Scaredy Cats - S2-E2
Continuity mistake: When Lisa's uncle shows her her grand-father's picture, it changes from one shot to another.
Diana Ross - S4-E23
Continuity mistake: When Diana Ross finishes her first song, the bird has both his feet on the ground; in the next shot, the bird has one leg raised, without enough time passing to do so. (00:08:45)
The Robbery - S4-E4
Plot hole: Towards the end, Jake (Shirley's boyfriend), hangs the girls on a coat rack by the hoods of their coats. They try a few comical ways of trying to escape, when they could have simply unbuttoned their coats and slip away.
Continuity mistake: In the close-up of putting the lids on the bottles, Mat's hands have 5 fingers (briefly done by a real person instead of the puppets). However, throughout the series, the duo is consistently 4-fingered - and that includes other close-ups that were also created with real hands briefly replacing the animation.