When Phyllis Newman is seen sitting up in bed with Jack Warden. She's holding a sheet to protect her modesty, but we can see her entire back down to her waist. But, when she gets up she's wearing a short half slip, that would have covered her back and been visible in that earlier scene.
When the VW is first seen it has a license plate of 2G-9193, but after it is hit by a taxi, the plate is 2G-9194 for the remainder of the movie (Of note, the characters do not change vehicles as this occurs during a driving scene).
While parking the red Volkswagen for the conversation between Jack Warden, Sorrell Booke, and George Segal, the side of the street they park on is lined with cars. But as they pull away after picking up Felix, that side of the street is empty all the way back to where the VW had been.
When the film starts and Morroe is shown in bed answering his phone after being awakened from a deep sleep, it's clear that actors George Segal and Zohra Lampert have not been in bed very long as the soles of their feet are obviously dirty.
Although Jewish tradition requires a closed casket, an open casket is seen as part of a plot point at a Jewish funeral.
A visible crew shadow is seen moving during the overhead sequence after the encounter with a taxicab driver, on the third film cut, as the handheld camera follows the car.