After Mary sprays whipped cream all over Dick's face, there's no whipped cream anywhere else. However, in the next shot, there's whipped cream on the door.
Near the end, as Dick and Mary are leaving the police station, a wall sign in the background hallway listing the room numbers of various City Hall departments has "Mosquito Abatement" listed at the bottom, with "Mosquito" spelled "Mosqusito".
When a player substitution takes place in basketball, the game buzzer is sounded. When Tommy is sent into the game there is no buzzer nor does Tommy check in at the scorer's table, which is also a requirement in basketball.
At 18:30, as Dick tackles the man who mugged him, the blue mat that they fall onto can be seen at the lower right edge of the screen.