Revealing mistake: As with many shows, the outside doesn't even come close to matching the inside layout.
Six Strangers at Apache Springs - S2-E7
Revealing mistake: During the saloon brawl, recycled footage causes Curry to change into his first season hat for a few shots. After the fight, he has his second season hat back on. (00:28:00)
Revealing mistake: At the end when Laurel and Hardy are licking Columbo, a substance is caked on Columbo's neck, presumably the food they used to get the dogs to lick Peter Falk.
Revealing mistake: During the opening theme, when the children are watching the magician, you can tell they were not actually filmed together. The magician scenes are filmed more professionally using a sharper tape or film image, whereas the children scenes look more like a standard fuzzier film-type such as on a projector (primarily used at that time).
Farewell My Beloved Witch - S1-E3
Revealing mistake: When Lupin is saved by Fujiko and is on the ladder, his lower left leg is missing. (00:21:05)