After Kramer gives his gift to Elaine and is speaking to Jerry, Jerry's door behind Kramer opens and closes between shots.
When Jerry and George are talking about the rules Elaine and Jerry established for their "friends with benefits", the sandwich on the table keeps changing.
When George (Jason Alexander) is suggesting gifts for Jerry (Jerry Seinfeld) to give Elaine, he picks up a picture frame and suggests getting it for her. After the camera cuts to Jerry and then back to George, the frame is back on the counter.
After Jerry asks Kramer to leave, his hands change positions between shots.
After Jerry and Elaine discuss the rule of the good night kiss, Jerry holds his hands together, but in the next shot his hand is over the couch.