Corrected entry: On the Seinfeld season 3 DVD, there is a feature called notes about nothing where along the bottom of the screen it tells you little notes about what is going on. Well in this episode it said they used mirrors to make their "parking garage" look bigger because a real one would be too expensive. When Jerry, Elaine, George, and Kramer enter the parking garage, you can see their reflections in a mirror in the top left area of the screen.
Corrected entry: In the episode when Jerry looks after Farfel the dog, George and Elaine are at the coffee shop, when they start making fun of Jerry. George asks Elaine if she's ever seen Jerry throw up, and she starts acting like she has seen him throw up. But she could not possibly have seen Jerry throw up because the last he did was June 29th 1980, years before Elaine and Jerry ever met.