Seinfeld (1990) - 3 mistakes in whole show

Continuity: Throughout the whole show, George Costanza is showed as being left-handed (eg. at the beginning of the episode titled "The Shoes", Jerry and George are writing "The Butler" script, and George can clearly be seen writing with his left hand). However, the actor himself is not, and you can spot some episodes (mostly in the first seasons) but a few in the last seasons as well, with him using his right hand for writing or eating, while in most of the show he's using his left-hand for everything.

Continuity: The exterior shot they use when establishing Monk's cafe is completely different than what is inside in the cafe. First the outside has neon lights with just RESTAURANT. The inside of the cafe, the menus, windows and door all have Monk's cafe logo on them. Secondly the door should be in the middle of the restaurant, instead the interior shows it to be to the left of the restaurant and somewhat to the side. Lastly the windows in the exterior shot are extremely large with no writing, logo and curtains pulled to the side. Inside the cafe, the windows are much smaller, with permanent curtains coming halfway up the windows and the rest being blocked by Monk's cafe logo.

Factual error: During the entire series, the view of Jerry's door from the hallway is of a flat wall with the door in line, yet from inside the apartment, not only does the kitchen angle into the hallway, but Jerry's fridge is recessed into the wall. The wall behind it should be blocking the hallway completely.