Character mistake: After Felix arrives at Oscar's apartment, he is looking out the window and comments on the view. He then asks, "What is it, twelve floors?" He had just come up in a self-service elevator, so he would have known what floor he was on.
Character mistake: Shortly after Felix arrives at Oscar's apartment, he goes to a window and asks if it's 12 floors. Oscar rushes over, slams the window shut, and says it's only 11 floors. Since Felix had to push the button in the self-service elevator to get to the correct floor, and since he had been to the apartment many times before to play poker, he would have to know that it was 12 floors.