When Voltan the magician points the gun at C. W. Briggs, he cocks it twice.
When C.W. is packing up to leave, he is carrying a box with a lamp and two picture frames. He hands the box to Sam and in the next shot, the lamp is tipped over and there are no more picture frames.
At about 2 min. 30 sec., CW asks his coworkers who won the sixth race at Aqueduct. After he gets his answer, one of them says, "Oh, hey, congratulations. I heard you recovered the stolen Picasso." But he only just told this to Mize seconds before, two offices and at least 50 feet away.
After returning to her apartment and waking up CW, Betty Ann turns on the radio and music plays immediately. However, the tubes in the radio hadn't been given any time to warm up.
The story took place in October 1940 and they were going to go to Paris for their honeymoon. The Nazis occupied Paris beginning in June, 1940.
At about 1 min. 55 secs., after CW makes his first appearance in the offices of the company, he says, "John, can I bother you for a minute. But the character's name is "Mize" (see the credits). "John is the actor's name.
The copy of "The New York Times" in the film lacks a hyphen in its name, although the hyphen wasn't dropped from "The New-York Times" until 1971.
Laura Kensington brings CW Briggs a bottle of Stolichnaya vodka, which was created in 1953 and introduced to America in 1965.
The Baldwin grand piano in the Rainbow Room has the modern logo, not the one the company used in the 1940s.
The train station called Grand Central in the film is in fact at Hoboken, operated by New Jersey transit.
When C.W. first meets the Coopersmith brothers, the reflection of the boom mic can clearly be seen in the upper right-hand side of one of the windows.
(around 27.47) The reflection of the boom mic is clearly visible of the photo frames behind Dan Aykroyd.
Laura Kensington tells CW she brought a bottle of Stolichnaya 120 proof, but Stolichnaya's only proofs are 80 and 100.
When being introduced by Voltan in his act at the nightclub, C.W. says he works for North Coast Casualty and Fidelity Insurance Company. The office door, however, reads North Coast Fidelity and Casualty Insurance Company.