Goofs

When in the hydrotherapy room, there is a recessed panel in the wall with two access doors, on the side of the room closest to where Mavis (Gail Strickland) is lying. At the beginning of the scene, both doors to the recessed area are open, but for the rest of the scene, the right-hand door is closed, even though neither Mavis nor Harper (Paul Newman) is close enough to it to have closed it.

When Mavis (Gail Strickland) and Harper (Paul Newman) are turning on the water to try to flood the hydrotherapy room, Mavis is first shown in close-up and there is no sign of the over-the-shoulder straps of her bra. But once the room is shown in a wide shot, and for the rest of the scenes in that room, she is wearing a bra with straps that should have been visible in the close-up.

When the fire hose is used in the hydrotherapy room, Mavis is initially left propped up unconscious in the corner while Harper is hosed down and struggles to get up. Once Mavis is hosed, she becomes conscious. The hosing stops, a short conversation ensures, and then the hose is turned on Harper again. During this scene Mavis is briefly shown as she was initially, unconscious and propped in the corner. This segment was clearly the continuation of the initial segment before Mavis was hosed.

The villainous Kilbourne, played by Murray Hamilton, has a catchphrase --- "That's outstandin'!" --- which he uses several times. However, when Harper (Paul Newman) mockingly mimics the phrase back to him, he does so at a point in the narrative when neither he nor the audience has actually heard the phrase being used.

While Harper (Paul Newman) and Mavis (Gail Strickland) are being hosed down in the hydrotherapy room, there are two empty bathtubs visible. The one on the left is clean, the one on the right is dirty. After Kilbourne (Murray Hamilton) leaves with his henchman Candy (Paul Koslo), a view of the same bathtubs reveals both to be clean.

The crew added a lot of air into the water coming out of the pipe in the floor to make it visible to the audience that water was flowing out of said pipe.

When Harper comes up the last time, from trying to turn the water off in the hydrotherapy room, his head bumps one of the ceiling panels and it clearly moves, meaning their attempts at breaking the panel were bogus.

At the beginning of the film, Harper struggles with Ford's then-new seat belt-ignition interlock safety system. He tried a few work-arounds, but then magically knows how to disable it by pulling wires underneath the driver's seat. Of course, this wasn't the real fix for this issue, as it actually involved a simple rewiring of a relay under the hood for most cars. Pulling wires as he did could have disabled the car completely.