Yes Sir, That's My Baby - S1-E19
Continuity mistake: In the scene in bus station, when Mork is talking to the drunk sleeping person, he's holding a bag, there's a shot of the FBI man, and the next shot of Mork, he's not holding the bag anymore.
A Case of Overexposure - S5-E8
Continuity mistake: In season one episode 16, Arnold says that him and Willis never met their landlord. In this episode they remember him as Mr Darcy - when they see him they recognise who he is.
Field Trip - S6-E6
Continuity mistake: When Roland plays his tape recorder on the coach, the woman on the tape says "lightest lemon sponge I've ever tasted - she used to bake, yes I remember, mind you she worked hard that woman..." But in the cafe Roland didn't start recording until she said "mind you she worked hard..."
Pink Arcade / Life With Feather (pilot) / Pink S.W.A.T. - S1-E2
Continuity mistake: Pink S.W.A.T.: the fly disappears on the magnifying glass before the pink panther smashes it. (04:00:03)