Continuity mistake: When Raymond finds Charlie and Susanna making love Charlie runs after him. A moment later we find Susanna soaking peacefully in a hot bathtub, without even nearly enough time to get in. Additionally, when they talk while Charlie is sitting on the side of the tub, wet strands of Susanna's hair appear in front of her shoulder. (00:33:10)
Continuity mistake: Near the end of the movie Raymond gets evaluated by Dr. Marston. When the doctor blames Charlie for kidnapping his brother his hands are on the table. When the camera angle changes to a side shot they are folded in front of his face, holding a pencil, and in the next shot they are down on the table again. Additionally, at the end of the scene a tray with water glasses gets shifted back and forth in alternating shots. (01:55:40)
Continuity mistake: After the duo stops at a motel with pink neon, Ray starts reciting his riddle about the guy on first base again, which gets Charlie annoyed and he badgers him over it. After their little exchange, Ray is walking up to the side of the car as Charlie opens the door to their room. Ray is standing very close to the car, standing right on the yellow line of the parking space. The camera then suddenly jump cuts to a higher angle and Ray is now several feet back standing in the middle of the next parking space over.
Revealing mistake: While Ray is driving the car, in the next shot of them driving down the road, you see a police car driving very slowly keeping back the traffic behind them.