When everyone is commenting on Kramer's jeans being too tight, he starts to walk away and Jerry says, "You're walking like Frankenstein".
* Frankenstein was the scientist who created life out of various body parts, but he was one whole human himself; Frankenstein's Monster was the one who is known to walk stiffly.
You can hear Carey Elwes's real accent when he says the date of his anniversary to Elaine.
Beth's Ex's apartment # is 5A and the door opposite says 5B, is it a coincidince that their door numbers are the SAME as Jerry's and Kramer's??? I think not!
Watch George's light blue button down shirt when he shows up at Beth's (Debra Messing's) apartment. His shirt is messed up from fighting through Elaine and Jerry to get out of Jerry's apartment to tell Beth that he was just being "folksy" instead of being serious about her being able to do a lot better than David as a husband. His collar goes up and down during the scene and oscillates between being tucked and partially untucked on one side obviously indicating the scene was shot more than once.
When Kramer goes into Jerry's apartment the first time after his performance with Mickey you can see a production mic at the top of the screen pretty obviously.
David: You know, as far as I'm concerned, this whole thing is George's fault.
Elaine: Well, David, the thing about George is that he's an idiot.
Kramer: I've got the body of a taut, preteen Swedish boy.