When Robert Tracey is stopped in traffic while driving his new sports car, he waves at Nina, his ex-wife, who is waiting at a cross walk. In the background there is a couple waiting in the inside lane and sitting in a convertible. However, when Tracey drives away when the light changes, there is no convertible in the inside lane.
Nina's martini glass moves from one hand to the other several time when she and Charlie are drinking martini's at the bar and again on the sofa
After Nina delivers the line 'Make me Laugh' Charlie is holding his Martini in his right hand and his cigarette in his left, in the next shot, he holds both his martini and his cigarette in his right hand.
Late in the movie when Charlie is visiting Nina at her home, Charlie and Nina walk over to the couch. It is too dark there and when Nina begins to sit down, the crew turns on an extra light to brighten the scene.
Walter Winchell's column spells the characters' last name Tracey, but doors at Robert's law firm spell it Tracy. Neither spelling is established anywhere else in the film, but they can't both be right.
When Nina and Rick are leaving Nina's Mother's apartment which is on Park Avenue in New York City, there is no median in the center of Park Avenue which separates the uptown and downtown traffic.
As Jack Lemmon pulls away from the stop light in his sports car, the car shifts gears while both his hands are on the steering wheel.