In the close-up of Ramon lying unconscious on the floor by the pool, there is a knee resting on a towel by his right ear (viewer's left) that was definitely not there before.
When George leaves the apartment in a rush to see Susan, Kramer holds his sandwich in both hands. It then cuts to a close-up of Kramer and his left hand is at his side.
When Kramer (Michael Richards) attempts to give Jerry (Jerry Seinfeld) the phone, his left hand is clearly empty. The next shot shows he suddenly has a newspaper in it.
When Ramon greets Jerry at his apartment and is introduced to Elaine, Ramon points at Jerry with both hands. In the next shot, Ramon's hands are by his side.
When Jerry says, "I think we should separate here" on the subway, Ramon's arms are hanging loose by his sides. In the next shot, he is holding onto the overhead rail.
Elaine and Susan discuss Susan B. Anthony's dress that she wore to the 19th amendment party. The 19th amendment was adopted in 1920. Anthony died in 1906.
When George calls Kramer's Movie Phone, Kramer tells him to enter the first three letters of the movie on his keypad. The movie was 'Chunnel' but when George is entering the letters he moves up on the keypad from the second to the third letter.