Continuity mistake: Close to the end when Edward Norton runs up to the front of the empty building and Brad Pitt appears, he tries to break the glass door by pushing a bench into the door, but it doesn't work. He doesn't move the bench and he then shoots at the glass and breaks it. When it shows him walking through the broken door, the bench has disappeared.
Trivia: There are several places where Edward Norton sees Brad Pitt for a split second before he actually meets him (not counting when he passes him on the escalator): By the photocopy machine, talking to the doctor, the testicular cancer group, Marla in the alley, and then when watching TV when the waiters say "Welcome". Also Tyler is the one who steals the Camaro, after Tyler and narrator meet for the first time.