Continuity mistake: In the scene in the restaurant where Tom Cruise and Dustin Hoffman are trying to order breakfast, Hoffman's character fixes the salt and pepper shaker a certain way. In the next shot they are opposite the way he fixed them. Then in the next shot they are back to the way he had fixed them. (00:37:15)
Continuity mistake: In the diner, after Raymond says the waitresses' phone number, the wide shot shows the napkin and cutlery next to the edge of the table. In the close up they are several inches to the left.
Continuity mistake: While Susanna gets out of the tub, dresses, and leaves the hotel room the wet patches on Charlie's undies first disappear and then reappear in a different pattern. (00:35:05)
Continuity mistake: In the diner, Charlie tells Ray to eat with a fork and moves his hand away. A frame later, a new angle shows the hand back in place and him repeating the movement.
Continuity mistake: In the train station, the brothers walk down a hallway with a man in a suit behind. He disappears in the following angle.
Continuity mistake: In the scene where Charlie and Raymond argue over K-Mart underwear an utterly frustrated Charlie stops the car, gets out, and vents his spleen. There is a close-up of the door opening with a clear vertical shadow, whereas all wide shots suggest that it's late evening. (00:54:05)
Continuity mistake: When Charlie tells Susanna about how he took the Buick for a ride and ended up in prison, the green blanket on the sofa where Susanna is sitting either covers the back smoothly or is pushed together alternatingly. (00:11:10)
Continuity mistake: While waving goodbye to Ray, a pair of blue jeans and white sneakers are seen behind Charlie, stepping up onto the train on the right. Immediately after, a wide angle reveals that the passenger is wearing shorts and darks shoes.
Continuity mistake: When Charlie has the brainwave to use Raymond's special abilities to make some money in Las Vegas they turn around and drive directly to Caesar's Palace, get dressed up, and make a lot of money. All of a sudden Susanna shows up, and we don't have a clue how she found out that they went there, when, on the other hand, we saw Charlie earlier calling his partner a couple of times, telling him his whereabouts, and even calling Susanna, when it didn't necessarily move the plot forward. (01:38:10)
Continuity mistake: After the toothpicks incident, Charles says "let's go" and turns his head to the right. In the following angle it's facing left.
Continuity mistake: When the girl hands Raymond the deck of baseball cards they are all messed and spread apart, but the opposite angle of him receiving them shows the deck neatly packed. (00:24:05)
Continuity mistake: When the brothers enter the train station, a fat woman in a blue suit with a brown briefcase exits the place. A second later she reappears in the hallway.
Continuity mistake: When exiting the station to meet the doctor, the brothers pass by a woman in white, when the angle changes they have moved 5 meters behind and pass by her again.
Continuity mistake: When the doctor is asking Raymond math questions, a blue car appears and disappears behind him.
Continuity mistake: When Charlie talks to Dr. Bruner in his office his right thumb is under his belt. When he is seen from behind the arm is hanging down, and when it cuts back to a front shot both his thumbs are under his belt. (00:17:00)
Continuity mistake: In the scene where Charlie Babbitt and Susanna are driving in a car and Charlie gets a phone call, telling him that his father died, you can see through the windows of the car, that they are driving through a town with many houses bordering the street. In the next shot from the outside, when the car is turning over, it's in a desert with no more houses around and a lot of windmills. (00:07:50)
Continuity mistake: After Charles calls Ray a r****d, the glasses and the cigarettes change position.
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: When Charlie comes back from Dr. Bruner's office and asks Raymond to get out of the car Susanna's hands are in her lap. When the camera angle changes her arms are up on the back and the side of the car respectively. (00:17:55)
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)
Answer: Susanna was there as well; Charlie just used the "date" as a reason for the three of them to go down for a drink together. He knew Iris wouldn't show up.