Revealing mistakes: The police radio that we hear in the background is LAPD radio transmissions, not Reno Sheriffs Department transmissions.
Audio/visual unsynchronized: In the episode where Jones is expected to lose his left ball, the gang plays around with their new bomb robot. When Jim starts to talk you hear him but his mouth is not moving.
Continuity: Trudy Wiegle's name changes from Wiegle to Weigle every so often
Errors made by characters (possibly deliberate errors by the filmmakers): In one episode while the cast is trying to guess what caused the injury to a victim, one of them guesses that it was the rumble of the controller of "the new PlayStation". The Playstation that was released shortly before the episode's air date was the first console in the series with controllers that don't have rumble.
Errors made by characters (possibly deliberate errors by the filmmakers): In the episode where Lt. Dangle and another guy get drunk in his squad car, the man asked "what gun is that? Is that a Glock?" and Lt. Dangle says "Yes, it's a Glock, 9mm." His gun is in fact a Beretta 92fs 9mm, not a Glock.