When Kramer (Michael Richards) takes the photograph of Jerry (Jerry Seinfeld). Jerry is turning to his left side. When we see the photo however, he is looking from the right.
When Jerry asks Elaine if Wendy is coming over, he takes off his jacket twice.
Kramer photographs Jerry with a Polaroid camera which takes pictures sized 3.1 in x 3 in with a border, saying later that he "took a double print". The photograph which he puts up in the lobby appears to be a 7 in x 5 in and has no border. It is not possible to take a double print from a Polaroid which has no negative.
When Wendy drops Elaine off after their trip, the blue screen outside the car is blue, rather than a street scene.
The photo shown in the lobby is not from a Polaroid, but an ordinary paper print. Additionally, Kramer (Michael Richards) took the photo from a distance whereas the photo is a closeup of Jerry's (Jerry Seinfeld) face.
Kramer decides to put all the residents' pictures up in the lobby of he and Jerry's building so everybody knows everyone else. While he hangs Jerry's picture in the lobby you can clearly see his own picture with only "Kramer" written under it. However, a resident ("Steve") comes down, presumably just coming to know Kramer from the picture and shouts "Hey, Cosmo!"
George says ketchup should be in a squeeze bottle since mustard is but it has been since the 80s and Leo even mentions the squeeze bottle to Nana.
Ketchup has been in a squeeze bottle since the early 80s.
There's a squeeze bottle of Hunt's Ketchup in the door of Jerry's refrigerator door when he's trying to avoid Wendy's kiss hello.
This contradicts the conversation between George and Jerry earlier.
Jerry (Jerry Seinfeld) & Uncle Leo (Len Lesser) are at Nana's (Billye Ree Wallace) house in order to open the ketchup bottle. They fight over who will open it & Jerry ends up letting Leo try. However he still can't open it and ends up handing it back to Nana. Conversation continues and the bottle is forgotten, but the whole point of them going over there was to open the bottle.