In the movie, when John Cusak and Billy Crystal are in the hotel where they are getting ready for the juncut, when you look at the number of the floor they are on it says one. But look the the left, and it says four. When they get the the fourth floor, it says four, but on the right it says one.
Billy Crystal is not in the movie 'Serendipity'. I think you mean 'America's Sweethearts' in which John Cusak is an actor at a juncit with an agent Billy Crystal, promoting his new movie co-staring his ex-wife, Catherine Zeta Jones.