Continuity mistake: In episode 64, "For Whom The Bell Tolls. And Tolls. And Tolls", Tracy is shown seated at the table with a bowl of cereal - but in the shots immediately before and after, she's not there, nor is there any food at her place. (00:01:10)
Continuity mistake: In an episode fairly late in the life of the show, Lou Grant says that when Mary came to interview for a job at the station, she bumped into the desk in his office and said, "Excuse me" to the inanimate object. However, we saw that interview in the very first episode, and no such thing happened.
Kitten Kong - S2-E7
Revealing mistake: When the Goodies are at the park with their animals, Graeme tries to teach his tortoise tricks. When the tortoise jumps, you can see the wire making it 'jump'.
Audio problem: Billie says her line "he needs a new image" without moving her lips.
The New Car - S4-E6
Audio problem: When Felix and Oscar are driving around looking for a parking space, Oscar says "let's sell the car." Felix then begins talking but no audio is heard, then an overdub of him saying "Are you crazy?" which doesn't match his lips.
Other mistake: Lou is wearing his US Army uniform, but he is displaying a US Marine Corps Rifle Expert Award on his uniform. (00:04:39)