Memories of Cab 804 (2) - S1-E12
Revealing mistake: The gang is talking about their experiences in Cab 804 but when Elaine's segment begins, Tom Selleck gets in the cab and the cab number is 264.
Visible crew/equipment: When Mork and Mindy are walking away from the lake after they first meet, there is a set of 8 lights in two rows of four in the background.
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.
Revealing mistake: When they switch over to a rock format at the station, Dr. Johnny Fever puts on the first record and sets up the needle. The needle then proceeds to ride across the entire record when it starts to spin all the way to the center of the record.