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.
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.