Revealing mistake: During the disco scene, Elaine is dancing with a fisherman who was just stabbed in the back. The fisherman has a knife sticking out of his back and you can clearly see the block that the knife is stuck in protruding from his shirt. There are holes from other takes too.
Trivia: Director Jim Abrahams has two roles in this movie. The first role was that of the bicycle rider that yells back at Kramer after Kramer hits him on the road. He also plays a role as a solicitor at the airport. He is the one who pauses after seeing how Kramer is treating the other solictors.
Continuity mistake: After you see all the newspapers talking about the plane, and when you see the drummer on TV who speaks by drum tones, when the drums are handed to him the ends of the sticks are round, but when he looks to HIS left, after the camera changes position, they're not round anymore.
Revealing mistake: In the flashback scene in the bar, one of the girl scouts slams the other girl scout onto the floor and one can see the mat that the girl lands on. It had been covered in dirt or dust but when the girl lands it is swept away and you can see one of the corners of the mat.