In an early-'90s, and again in late 90's/ early 2000's, Spinal Tap tour, Michael McKean, Harry Shearer and Christopher Guest opened for themselves as The Folksmen and were booed during the first act, as people did not know or cared that the two bands had the same musicians.
According to an interview on NPR, a number of real folksingers from the '60s, including Arlo Guthrie, wanted to be in the movie, but the producers thought that would detract from the satire value and declined.
The early sequence in which the Folksmen rehearse for their reunion concert at a farm in upstate New York was inspired by the documentary The Weavers: Wasn't That a Time (1982), in which the real-life folk-music group The Weavers were shown preparing for a reunion concert at the upstate New York farm owned by one of their members, Lee Hays.
According to an interview with Michael McKean's wife Annette O'Toole, the songs were written by her and McKean during a car journey to Vancouver from their home in LA. Planes were grounded following the terrorist attacks on the USA on 11 September 2001 and O'Toole had to get to Vancover to film her TV show Smallville (2001).
Mickey's new husband is a model train enthusiast with only one train. This is because when the filmmakers went to the home which supposedly contained an impressive train setup, all of the trains themselves were broken or otherwise unusable. The engine seen moving in the movie is being pulled by dental floss through "Crabbe Town".
John Michael Higgins wrote all of the vocal arrangements for The New Main Street Singers. Originally the group was going to be a nine-piece ensemble that sang in unison (everyone singing the same part) but it was decided to give Higgins free rein with it.