Continuity: The salt and pepper shakers at the first diner.
Continuity: In Raymond's final evaluation scene, the tray of glasses in the middle of the table moves back and forth.
Crew or equipment visible: Reflection of crew members on the hood of the Buick when Raymond is about to drive in Las Vegas.
Continuity: When Susanna gets mad at Charlie and storms out of the tub, Charlie's sweats have a different pattern of water splashes than when she goes out the door.
Continuity: In the laundromat the dryer on the left of Raymond is closed/open between shots.
Continuity: Raymond takes pictures throughout the movie with a 126 film camera. We see, under the credits, the pictures he had taken and they are all rectangular in shape, when 126 film makes square pictures.
Errors made by characters (possibly deliberate errors by the filmmakers): While watching Charlie play blackjack, one of the casino security officers says that "no one can count through a six deck shoe". In fact, this is quite possible for someone with just basic math skills to do using the "hi-lo" counting method. A security officer of any major casino should know this.
Factual errors: The story line states that 8,095 Buick Roadmaster Convertibles were made for 1949. This is incorrect; the actual total is 8,244.
Crew or equipment visible: When Charlie, Raymond and Susanna are in the casino on the way to Raymond's date, just before Charlie is asked to see head of security you can see in the mirrored pillar the reflection of a woman motioning extras to walk past the camera.
Continuity: At the blackjack table after Raymond "takes" Charlie's queen, Charlie doubles down with more chips than he originally bet. Double down bets are limited to the amount the player bet originally; you can double down for less than you originally bet, but never for more.
Errors in geography: Charlie and Raymond are shown to be driving west first on Columbia Parkway shown by the wall in the background that is on the North side of the road. If they are driving from left to right as shown in the movie, then they are driving West. Then it shows them driving East down a small hill into the neighborhood Columbia Tusculum. They are supposed to be heading to California. California is west and it last shows them driving East. Charlie and Raymond are driving in the wrong direction.
Errors made by characters (possibly deliberate errors by the filmmakers): Rain Man says that he buys his underwear at K-Mart on Oak & Burnet. There isn't a K-Mart located on Oak & Burnet. Oak & Burnet is the location of the Vernon Manor Hotel, where Tom Cruise and others in the cast stayed during the filming of the movie.
Continuity: While Raymond and Charlie are seated in the 'toothpick' restaurant scene, the salt and pepper pots change position several times.
Errors in geography: Laundromat scene was supposed to be in Tucumcari, N.M. The town of Tucumcari is larger and has no tall, red-rock mountains in the background. It's on the edge of the high plains, but does have some small mesas west of town.
Errors in geography: From the time they left the farmhouse in western Oklahoma, they supposedly passed some country with mountains in the background (west) between there and Amarillo, Texas. There are no mountains in that part of western Oklahoma (though some small ones exist farther south near Lawton and Altus) - and the nearest "mountain" on that route would be Tucumcari Mountain.
Continuity: The card scheme with all the Queens is repeated several times during the course of Charlie's play.
Factual errors: "The People's Court" and "Wheel of Fortune" are syndicated TV shows, and, therefore, air at different times of the day in different TV markets - abut Raymond is able to watch them at the same time each day (a change in the TV schedule would have been traumatic for him) during his cross-country trip.
Factual errors: While crossing the Suspension Bridge in Cincinnati (the 'singing bridge' that Raymond hums along to), the traffic in the background suggests that the bridge is either 4 lanes, or a one-way street. In fact, the bridge has only 2 lanes, one northbound and one southbound.