Corrected entry: When Jelly is showing Dr. Ben all the weapons at their disposal he asks if he know how to shoot an AK then he asks about the Kalashnikov. AKs and Kalashnikovs are the same thing.
Corrected entry: When Billy Crystal is leaving the jail after picking up Robert DeNiro, we see the SUV driving away, but with only Billy in the front seat of the car. When we get another camera shot, we see DeNiro sitting in the passenger seat.
Correction: I've watched the scene over and over and if you look careful enough you can see Robert DeNiro sitting in the passenger seat. You may have not seen him because of the darkness inside the car but you can see him in the passenger seat when the car passes by the camera. You can even see the paper bags on his lap.
Corrected entry: When Paul is attempting to be a car salesman, he becomes flustered that the couple he is talking with are driving a Lexus. He begins ranting about the Lexus being a Toyota, about Pearl Harbor, etc. However, after his entire anti-foreign, pro-American car speech (which does not get him a sale), we see that he is not selling American - he is selling Audis.
Correction: This is not a pro-American rant that Vitti went on, he was just trying to convince the couple not to buy a Japanese car because of what happened in Pearl Harbor, thus buying an Audi wouldn't support the Japanese market (it wouldn't support the U.S. either but either way it's one less Japanese car on the road). So Vitti isn't necessarily a hypocrite.
Corrected entry: In the scene where Robert De Niro is selling jewelry to the couple, he turns his head to the side and we can see that he is wearing nothing on his head, yet near the end of the scene (as he walks away from the couple) he is wearing a kippot (a Jewish head covering).
Correction: This (I'm sure) is deliberate as De Niro is fantasizing about all sorts of crimes in this scene only to leave the store being a model Jewish citizen, just like his boss who is looking at the diamonds.
Correction: Kalashnikov made the original AK-47 (still does), as well as many other models of guns. There are a lot of companies making knock-offs of the AK, including American companies. It's very possible the AK he was talking about could have been made in China, for all we know, and the Kalashnikov was an actual Kalashnikov branded gun.