When Jerry is done driving his father and mother back to his apartment, he takes off his jacket twice.
Five minutes in, a water bottle can be seen on the table in front of Kramer (Michael Richards) & Morty (Barney Martin) From shot to shot, its location on the table changes -- in one shot, it is close to Morty, in the next, it is farther away. This happens throughout the scene.
When Jerry, his parents, and Kramer are in Jerry's apartment, Kramer is seen drinking from a can of Pepsi. Later in the hallway, with the Pepsi can still in his hand, Kramer spits out what he has been drinking after being surprised by Jerry. The liquid is transparent, not brown as colas should be.
When Jerry and Kramer are talking in the hall and Kramer is holding a can of Pepsi, the can vanishes at the end of their conversation.
Morty's x-ray has a label that changes sides between shots, and at one point completely disappears then reappears.
During the filming of the scene in which Kramer accidentally sets his hair on fire, Michael Richards wore a wig to protect his scalp. When he ran into the bathroom, the wig fell off causing the cast to laugh. They can be seen beginning to laugh just before the scene is cut.
At one point, Kramer is using the stove to light his cigar, but when he stands up there's smoke coming off the top of his hair, even though that part of his head was nowhere near the flame that lit the cigar.