Kramer's sleep schedule equals 4 hours a day making
It 12 hours in 3 days not an hour and half like Jerry said.
When Jerry and Elaine talk in her office, he picks up a sandwich and starts to eat. Around the time Bob walks in, a napkin appears in Jerry's hand from nowhere.
When Connie starts to kiss Kramer on the neck, she starts at the base and works up to his jaw. In the next shot, she is back at the base.
When Kramer is thrown into the water, the sky is pitch black. In shots of the incoming ship, the sky behind it is lighter.
When George comes in to tell Jerry the wedding date, a roll of paper towels on the counter changes position between shots.
When the group go to the Santos Brothers' (The Flying Karamazov Brothers) dressing room, the brother who answers the door says that two of his brothers have already left, and we see there are two more brothers in the room. That's a total of five brothers, yet we only see four on stage.
When Jerry and George see one of the Sandos brothers wearing a blue jacket at The Friar's Club, they mistake the jacket for the one Jerry wore the night before. Since Jerry was given a jacket by the club, it is possible that the club gave the Sandos brother a similar jacket and that he was not necessarily wearing the jacket Jerry wore to the show.