Revealing mistakes

Throughout the series when we see a closeup of CGB Spender's/The Smoker's ashtray while he is extinguishing his cigarette, the filters of the "smoked" cigarettes already in the ashtrays are perfectly white, while they should be yellow/brown from the nicotine-smoke. This indicates that they are props, placed there before shooting and not cigarettes smoked by the characters.

Errors in geography

In numerous episodes in the earlier seasons, characters are seen driving cars with British Columbia License plates.