At one point during the production, Liza Minnelli is supposed to board a bus in front of Bergdorf's on Fifth Avenue. When a real bus came along, she boarded it thinking it was the "movie bus". Not until she was halfway down the block did she realize her blunder when she looked back and saw the whole crew cracking up.
Apparently, writer-director Steve Gordon had originally wanted to cast George Segal in the lead role of Arthur. After the box-office success of 10 (1979) however, Dudley Moore replaced Segal. This movie was actually the second time that Moore replaced Segal. Segal was originally cast in the lead role in 10 (1979) but Segal apparently walked off the set shortly after filming began. Reportedly, this was rumored because Julie Andrews' role had been built up. Apparently, after 10 (1979) had been released, Segal, when once asked if he had seen the movie, allegedly replied with a finger gesture.
The scene where Arthur drives his "racing car" around a track was shot at the now defunct Danbury Fair Racearena in Connecticut. The type of car that Arthur drove was never raced there, it was primarily for Modified stock cars and was one of America's great short tracks. Sadly, despite its great success, the land became too valuable and it gave way to a shopping mall. The Danbury Fair Racearena closed on October 12, 1981, shortly after the movie was filmed.
This movie is the only ever theatrical feature film directed by Steve Gordon. This movie's sequel Arthur 2: On the Rocks (1988) is dedicated to the memory of Gordon who died in late 1982 which was only about eighteen months after this picture had debuted.