When Arthur puts his giant martini down on the counter, Happy can be seen in the background pulling it towards him. A second later when he and Emily are seen from the front talking, the martini glass is nowhere to be seen. It is too large to not be in the shot.
When Maurice (Oliver Platt) goes in the bakery to insult the baker and tell him His pastries are stale he is offered a cream puff to taste, he then stuffs it in his mouth which amounts to some being dropped on his lapel, in the next shots his lapel is clean.
When Happy Franks sits at the bar and sees the sleeping pills, the bottle has the address printed on it, including the ZIP code. ZIP codes were not used until 1963.
During the opening scene in the park café, modern cars are passing by in the background.
The song, "Skokiaan" is used in the movie which takes place in the 1930s. However, "Skokiaan" was not released until 1947.
Though the song "I Get Ideas" was scored in 1927 as "Adios, Muchachos", the lyrics to "I Get Ideas" were not written and recorded until 1951. The film takes place in the 1930s.