* DuelingMovies - With ''Film/{{Twins}}''.
* MethodActing: DustinHoffman's portrayal of Raymond changed so much over the course of making the film that by the time the second half was filmed, they had to re-film the first half because Hoffman's portrayal had improved so much. Hoffman worked with Kim Peek for a while to try and understand him. Hoffman later suggested they let Kim interact with the public more via forums as he saw a big improvement with his social skills after only a few days of interacting with a stranger. Kim (with his father and caretaker) started doing conventions and because of this movie he was in high demand and very popular.
* WhatCouldHaveBeen: Among other people envisioned for the role of Raymond: Creator/BillMurray! Just try to wrap your head around that.
** Creator/StevenSpielberg was supposed to direct, but he had to drop out due to his commitment to ''Film/IndianaJonesAndTheLastCrusade''. He gave the notes he had made in preparation to Creator/BarryLevinson.
** Raymond was also originally written as a higher-functioning, extroverted autistic man. It was Hoffman who suggested making the character a more severe, introverted autistic, and they ran with it.
* WriteWhatYouKnow: Writer Barry Marrow based Raymond on a real life Autistic man he met. He admits that he took the man away from the institute and took him on a road trip.