Factual error: Near the beginning of the film, a scene opens with the subtitle 'New York'. Strange, these New Yorkers drive on the left.
Revealing mistake: Right at the start there is a TV 'clip' showing the crowds outside the Lyceum. This is supposedly 1974 but you can quite see a pretty modern looking CCTV camera above the Lyceum door.
Factual error: Although the 1984 scenes are supposed to take place in New York, there are obvious shots of red double-decker buses and other London trademarks.
Continuity mistake: When Arthur first goes into his room with the new Brian Slade record, you see him lodge the top of his chair under the knob of his door, but after he starts the music, they show him laying down on the carpet, and you can clearly see the top of the chair facing away from the wall.