Goodbye, Farewell, and Amen - S11-E16
Other mistake: How did Hawkeye Pierce, a surgeon, know how to drive a tank? It is nothing like driving a car and takes skills, training and experience that a surgeon simply would not have. He wouldn't even be able to start the engine.
Continuity mistake: When Fred takes his plate from one room to the next, they switch from a small object on the plate in the living room to a full size Danish when he walks into the kitchen screen.
Not with My Sister You Don't - S1-E19
Character mistake: Howard Borden goes to Bob's office and says it's the first time he's been there. In fact, he had come to the office to address Bob's "fear of flying" group in the first episode.
German Week - S3-E6
Revealing mistake: When Mr. Humphries and Mr. Lucas make their toast with the German mugs, Mr. Lucas' mug breaks but Mr. Humphries' does not. A moment later, when Mr. Humphries notices the mug has not broken, you can see that he crushes the mug with his hand.
Continuity mistake: Just after Otis makes the ghost sounds from inside the house, it shows the gang standing together outside the house. Otis is with them outside, which is impossible, as he is inside the house pretending to be the ghost.
El traje del tío Jacinto - S2-E16
Visible crew/equipment: In the credits, there's a unknown person hiding behind Don Ramón (Raymond).
Continuity mistake: Towards the end of the episode, Maude makes Walter breakfast and lists some things she will get done around the house. One is to paint the kitchen chairs. She spray paints the chair with Walter in it - the amount of spray paint on Walter's jacket changes thoughout the scene, especially when Maude is on the phone turning down a job.
Blödeln auf die feine englische Art - S1-E2
Other mistake: In the "Happy Valley" segment, when the witch is just about to enter the cathedral, you can see a car drive past through the windows behind the altar. (Now, this is Monty Python, so we have to be careful... But is isn't clear, or funny, enough to be there on purpose).
Continuity mistake: When Batman and Robin guest star on the show, Batman's cowl changes from covering his neck to exposing his neck.