Revealing mistake: One of the party guests opens the door of the fridge and you can see behind the set instead of looking into the fridge. (00:32:40)
Galactica Discovers Earth: Part 1 - S1-E1
Revealing mistake: When Troy and Dillon land on Earth, they take their bikes onto the freeway. They're followed by a large group of curious bikers. When two of the bikers move alongside Troy and Dillon and start talking to them, it's obvious that all four bikes are now mounted on a trailer, instead of riding on the road. Easiest way to tell is that their heads are higher up than the other bikers and the front wheel isn't turning.
The Compassionate Society - S2-E1
Revealing mistake: At the beginning of the episode, MP Jim Hacker's chauffeur is driving him across London. You can see in the background that the car is moving around London, but the chauffeur is not driving it. You can't see his hands and the steering wheel never moves.