Factual error: Charlie was at Mayview State Hospital typing by the window. In the not-too-far distance, the University of Pittsburgh's Cathedral of Learning is visible. Mayview was located in Bridgeville, PA which is about 15 miles away, so The Cathedral shouldn't be visible. (Pittsburgh's terrain is hilly - not flat enough to see very far). (01:33:40)
Factual error: In all of the cafeteria scenes, the food pyramid posters that can be seen on the walls are the updated 2011 versions, not the ones they would have had in 1991 and 1992.
Factual error: Whenever Charlie, Patrick, and Sam go through the tunnel into the city, you can see "Consol Center" on the road sign. The Pittsburgh Consol Center was built in 2008, but this movie's set in the 90s.