Continuity mistake: CC opens the door to Mr. Kirkeby who is back for the galoshes; you can see Jack Lemmon casting a pronounced shadow over the light switch by the door in the close-ups, but in the wider shots of the room Kirkeby is searching and then exits, that shadow is not showing, just one on the door itself. (00:06:45 - 00:07:30)
Continuity mistake: Baxter meets his neighbour for the first time as he is about to unlock the door. In the very first shot the doc lowers his arm, which is raised again in the close-up. (00:08:30)
Continuity mistake: In the first elevator scene, when Shirley MacLaine calls the floor number (19), between her, Jack Lemmon and the wall there are a man with a fedora reading the New York Times, and a woman with a turban. When the elevator doors open and people come out of the cabin, the woman is nowhere to be seen. (00:17:05)
Continuity mistake: During the second round of drinks, the amount of ice left in the frozen daiquiri changes depending on the camera angle. It's poofy and opaque in the side view, and deflated and almost fully transparent in the tighter close-up on Shirley MacLaine, with an intermediate angle and state. (00:38:10)
Continuity mistake: To revive Fran, Dr. Dreyfuss slaps her repeatedly and breaks capsules for her to smell. One of the capsules is on the armrest of the chair, and it is positioned and tilted differently each time a cut intervened with Jack Lemmon going to the windows and back. (01:09:00)
Continuity mistake: During the sequence when CC and Fran are playing gin with her recovering from the sleeping pills, close-ups of Shirley MacLaine have hard light come from her left side, while the wider shots with Lemmon in it have light coming from (her) right side. (01:25:00 - 01:28:10)
Continuity mistake: It was not a suicide attempt after all, and much relieved, CC grabs the bag of groceries to bring it inside the kitchen. He is carrying the bag to his right with the torso tilted, but in the reverse shot here he is, tilted in the opposite direction, the bag weighing against his left side. (01:37:45)
