Other mistake: When the show aired in 1990, in the pilot episode Brenda falls for Jason. She later on reveals herself to be a "16 year old junior" in high school. Season 2 opens up with the gang on summer break which technically would make them going into their senior year. It wasn't until Season 3 that they were going into their senior year. They graduated in 1993 from West Beverly but the show debuted in 1990 so technically they should have been sophomores.
Other mistake: When they are showing the rap sheets for the Cambodian man, the race on the sheet says Caucasian when he is Asian, and for the African American man, the sex says "F" when he is male.
Other mistake: When Cooper is on the floor after being shot, as he's signing the check, he is doing so with the pen closed, and proceeds to click it open as he hands it back to the room service.
Did the Earth Move For You? - S2-E1
Other mistake: Viv and Phil are waiting in his office for the power to come back on after the earthquake, but you can see lights on in the building across the street. (00:16:30)
Other mistake: When Fay is talking to Lowell over the walkie talkie, when she is giving him the recipe she is not pressing the button to talk, but Lowell still responds.