Other mistake: Mainly in "Who Stole My Watch?" and 2 other episodes the the Petries and the Helpers talk about the Helpers dog, but there is no dog, the dog doesn't have a name they keep saying "our dog" or "their dog", and there's no dog house, water bowl or food bowls for a dog at their house in any episode.
Other mistake: Any time Rob has to go to a doctor or to Jerry to get his teeth worked on, if you look at the window behind him and whoever is working on him. It's the same buildings every time. Even though he goes to different doctors. Also, that window and the curtains are also the same exact windows and curtains in Robs office.