It is said before the field trip that one of the group has not left the hospital in twelve years. As the story progresses, the viewer learns that Billy (Michael Keaton) has been there for a year and a half and Henry (Christopher Lloyd) for two. Later, Jack (Peter Boyle) visits his old office and most people remember him, implying he hasn't been gone for more than a few years. This leaves Albert (Stephen Furst) as the long-term patient, the only one of the group, about whose earlier life, nothing is revealed.
Some movie posters for this film featured a long blurb that read: "This morning they were playing ping-pong in the hospital rec room. Now they're lost in New York and framed for murder. This was never covered in group therapy. The Dream Team. Four guys on a field trip to reality."
Billy (Michael Keaton) jokingly tells the shopkeeper that he and his group are a special combat unit with the U.S. Marine Corps after some Libyan terrorists. This may be a reference to Back to the Future (1985), where Libyan terrorists were after Christopher Lloyd's character, Doc Brown.
This movie's title (The Dream Team) would become the nickname for the U.S. National Men's Olympic Basketball Team three years after this movie came out. The name would be permanently associated with the basketball team.
The place where the hospital inmates went on a day trip to see a baseball game was Yankee Stadium. The venue was closed in 2008 and demolished in 2010. The site where the sports arena existed is now parklands.
At one point, Jack McDermott (Peter Boyle) says: "I was pulling down one hundred big ones a year when you and Satan were out chasing Daryl Hannah!" In the following year after this movie launched, Hannah co-starred with Dudley Moore in a psychiatric comedy of her own, Crazy People (1990).
All three characters that Michael Keaton played in movies in 1989 were all 'B' names, with first names beginning with that letter. They were Billy Caulfield in this film, and Batman and Bruce Wayne in Batman (1989).
In the music video for the soundtrack song "Hit The Road Jack", not only are there various clips from the movie being shown in the background, Peter Boyle and Stephen Furst show up as their characters Jack and Albert, dragging Buster Poindexter (David Johansen) into a red van like the one from this movie.
Jack (Peter Boyle) says, "Wah Wah Wah", impersonating the sound in a cartoon when someone gets tricked or outwitted. Working with the same director, Howard Zieff, in Slither (1973) (with James Caan), Boyle did the same sound.