At the beginning of the movie, Katie walks into a bar with Bill. They agree that Katie will have her usual, Dubonnet on the rocks. Bill disappears for a moment, then returns with Katie's drink, which has absolutely no ice.
At the very end of the movie when the camera is behind Katie as she reaches up to touch the front of Hubbell's hair, he grasps her wrist with his right hand. When the shot immediately switches to behind Hubbell, his hand is not on her wrist.
At the end of the movie, Barbra Streisand and Robert Redford embrace. He's wearing a trench coat with the collar up. In the course of the embrace, shot from behind Redford, Streisand's gloved hand moves down the back of his head, ultimately flattening the collar of the trench coat. In the next shot, face-on to Redford, the collar of the trench coat is back up.
Near the beginning of the movie Hubble is dancing with Katie you can see her pearl ring on her finger go from the pearl centered on her ring finger to the ring turned and the pearl is down next to her little finger and then the pearl is centered again on her finger. It also looks like the ring changes size from fitting her snuggly to being loose then fitting snuggly again.
At the beginning of the film when there is a montage that depicts how athletic Hubbell Gardner is, there a shot showing a birds eye view of him throwing the discus. He throws the discus out of the throwing circle traveling from one side of the circle (9 o'clock) and sees him release the discus at the other side (3 o'clock). The correct position for releasing the discus is clearly marked on the circle at the 12 o'clock position.
In California, Katie is holding a "hot" pot and offers it to Hubble. He takes the spoonful and notes that it is indeed hot. However, moments later, Katie is holding the bottom of the pot with her bare hands.
In Katie's apartment the first time Hubbel visits Katie prepares hot water for coffee, as she leaves the kitchen it is clear that the top of the kettle is on crooked. As she enters the bedroom where Hubble is sleeping in the bed the kettle starts to whistle which startles Hubble. The kettle would not have whistled with the top lop-sided.