After Jerry tells Elaine and Landis that Newman is a fantastic tennis player, it cuts to a different angle and Jerry is already walking away from them in a different direction.
Jerry claims that apartments did not exist in Medieval times, but in fact the concept of the apartment dates back to ancient Rome.
In the final scene as Kramer leads the gang down the hall to unlock Newman's apartment, he clearly looks at the camera.
In Jerry's apartment, after he concludes nobody can do the switch, cameras are clearly visible in the vintage Porsche poster above Jerry's right shoulder. The camera's red light can be seen panning from L to R as Jerry moves.
Ms. Landis says she tore her "humeral epicondylitis", but humeral epicondylitis is a syndrome describing inflammation of the elbow tendons, and is not a muscle itself.