Glenn Close plays Robin Williams's mother, yet she is only four years older than he. Similarly, Close and actress Mary Beth Hurt played women from successive generations yet in real life they are only aged one year apart.
The initials of T.S. in Garp's name stand for "Technical Sergeant" and are based on the name and rank of his father in the army, who was only known as Technical Sergeant Garp, a ball turret gunner (tailgunner). The initials also can form a literary reference to T.S. Eliot.
The name of the feminist group of women who cut out their tongues as a show of protest and solidarity was the Ellen James Society, informally known as the "Ellen Jamesians". The Atlanta Rock Band "Ellen James Society" based their name on this fictional group.
The house that the plane crashes into was built at one end of the only runway at Lincoln Park Airport, a very small airstrip in Lincoln Park, NJ USA (about 35 miles NW of New York City). The wrecked house was not removed for several weeks. While no planes have hit houses in the vicinity, one did bounce off the roof of a passing car several years earlier.
Glenn Close landed the role of Jenny after director George Roy Hill and casting director Marion Dougherty had seen her in a Broadway production of "Barnum" opposite Jim Dale (1980). Close got Oscar nominated for this film for Best Supporting Actress, getting the nomination for her debut performance in a motion picture feature film. The nomination was the first of many bridesmaids for Close who thirty years later [August 2012], and after six nominations, is still yet to win an Academy Award for acting.
This film was made and released about four years after the novel of the same name by John Irving was first published in 1978. The book was Irving's fourth novel, its original title being "Lunacy and Sorrow". The book was a 1979 finalist for the National Book Award for Fiction and in the next year won the 1980 National Book Award for Paperback General Fiction. The picture was the first filmed adaptation of an Irving book and was also the first of two Irving adaptations that were released in the early 1980s, the second being The Hotel New Hampshire (1984). In the latter, as in the book, a dog named "Sorrow" dies in a plane crash.
The title of Garp's mother Jenny Field (Glenn Close)'s partially autobiographical book was "A Sexual Suspect", its dust-jacket title being "Sexual Suspect: An Autobiography". The title's of the books that T.S. Garp (Robin Williams) wrote in the film were "Procrastination" (his first); "Second Wind of the Cuckold" (his second); and "Ellen" (his third). The name of the novel that T.S. Garp wanted to write with the assistance of Walt and Duncan was "A Child's Christmas with a Whale" whilst the name of the short story that graduate student Michael Milton wrote in Helen's class was "Black Snow". In John Irving's source novel, the title's of T.S. Garp's novels were mostly different to the film's, they were "Procrastination"; "The Pension Grillparzer"; and "The World According to Bensenhaver".
Transsexual Roberta Muldoon (John Lithgow)'s original name before her re-assignment when she was a he, a male gridiron footballer, was Robert Muldoon. The team he played for was the Philadelphia Eagles, his player number was No# 90, his player position, a tight end.
The trivia item below may give away important plot points.
The famous final line of John Irving's novel "The World According to Garp" reads: "In the world according to Garp, we're all terminal cases". The final line of the film is different, it states: "I'm flying".