[4] Filmmaker Martin "Marty" Di Bergi is filming a documentary about English rock band Spinal Tap's 1982 United States concert tour to promote their new album, Smell the Glove.

The band comprises childhood friends David St. Hubbins and Nigel Tufnel on vocals and guitar, bassist Derek Smalls, keyboardist Viv Savage, and drummer Mick Shrimpton.

Tensions rise between the band and their manager, Ian Faith, as several shows are canceled due to low ticket sales, and major retailers refuse to sell Smell the Glove because of its sexist cover art.

Before they go on stage, Nigel arrives and tells them that Spinal Tap's song "Sex Farm" has become a major hit in Japan and that Ian wants to arrange a tour there.

Ian is rehired as the group's manager, and Spinal Tap (now with Joe "Mama" Besser as their drummer) performs a series of sold-out shows in Japan.

During production of that sketch (while being burned with oil from an on-stage effect) McKean and Guest began to improvise, inventing characters that became David St. Hubbins and Nigel Tufnel.

[6] Rob Reiner procured $60,000 from Marble Arch Productions to write a screenplay with McKean, Guest and Shearer, based on the Spinal Tap characters.

They realized after a few days of writing that no script could capture the kind of movie they wanted to make, so they decided instead to shoot a short demo of the proposed film.

Smokler had great instincts for camera placement on set, according to Reiner, and is responsible for the film's handheld cinéma vérité style[9]—although the cinematographer did not understand what was supposed to be funny about the movie.

[9] The scene where Spinal Tap becomes lost backstage was inspired by a video of Tom Petty at a venue in Germany, walking through a series of doors trying to find the stage, but ending up on an indoor tennis court.

"[12] According to Harry Shearer in the Criterion edition DVD commentary, keyboard player John Sinclair had just returned from touring with Uriah Heep when principal photography was about to begin, and told them how they had been booked to play an Air Force base.

In post-production, Christopher Guest was very concerned with the verisimilitude of the finger positions on the band's instruments during the concert scenes, and even re-shot some footage after the movie was edited to ensure their hands appeared in sync with the music.

[6] The character of Jeanine, David's disruptive girlfriend, was added during the production to provide a storyline to the material—in part to mollify studio executives who worried the movie would be plotless.

The site's critical consensus reads, "Smartly directed, brilliantly acted, and packed with endlessly quotable moments, This Is Spinal Tap is an all-time comedy classic.

[19][20] Gene Siskel of the Chicago Tribune also awarded four out of four, writing, "It is so well done, in fact, that unless you are clued in beforehand, it might take you a while to realize that the rock group under dissection in This Is Spinal Tap does not really exist.

"[22] In 2002, This Is Spinal Tap was deemed "culturally, historically, or aesthetically significant" by the Library of Congress and was selected for preservation in the United States National Film Registry.

David Ansen from Newsweek called the film "a satire of the documentary form itself, complete with perfectly faded clips from old TV shows of the band in its mod and flower-child incarnations".

[24] Even with cameos from Anjelica Huston, Billy Crystal and Patrick Macnee, Spinal Tap still managed to trick many of its moviegoers into believing the band existed.

Jimmy Page, Robert Plant, Jerry Cantrell, Dee Snider and Ozzy Osbourne all reported that, like Spinal Tap, they had become lost in confusing arena backstage hallways trying to make their way to the stage.

U2 guitarist The Edge said in the documentary It Might Get Loud that when he first saw Spinal Tap, "I didn't laugh: I wept," because it summed up what a brainless swamp big-label rock music had become.

[33] In their respective Behind the Music episodes, Quiet Riot's Rudy Sarzo and Ratt's Robbin Crosby compared their own bands to Spinal Tap to some extent.

For example, as a parallel to the "Shit Sandwich" incident, Quiet Riot's fourth album Condition Critical was given the two-word review of "Prognosis: Terminal" by J. D. Considine in Musician magazine.

's Mike Mills described the band's early tours as "very Spinal Tap", citing, among other things, they had played at a United States Air Force base.

Judas Priest, the heavy metal band that Rob Reiner saw in preparation for the film, has had many drummers in its career (eight in total), which the website Ultimate Classic Rock described as "positively Spinal Tap-worthy".

[46] In February 2017, Shearer's co-stars Christopher Guest and Michael McKean, as well as the film's director Rob Reiner, joined the lawsuit against StudioCanal and Vivendi, seeking $400 million in damages.

[54] It included an audio commentary track with Christopher Guest, Michael McKean and Harry Shearer; a second audio commentary track with Rob Reiner, Karen Murphy, Robert Leighton and Kent Beyda; 79 minutes of deleted scenes; Spinal Tap: The Final Tour, the original twenty-minute short they shot to pitch the film; two trailers that feature Rob Reiner showing a film about cheese rolling (because "Spinal Tap" itself was still in the editing room); a TV promo, Heavy Metal Memories; and a music video for "Hell Hole".

In 2000, MGM Home Entertainment released a special edition with more or less the same extras from the Criterion edition, plus a new audio commentary track with Guest, McKean and Shearer performing in character throughout, commenting on the film entirely in their fictional alter-egos, and often disapproving of how the film presents them; 70 minutes of deleted scenes (some of which were not on the Criterion DVD); a new short, Catching Up with Marty Di Bergi (where it is revealed that the members of Spinal Tap were very disappointed in Di Bergi for making a "hatchet job" of their film); the Heavy Metal Memories promo and six additional TV promos; music videos for "Gimme Some Money", "Listen to the Flower People" and "Big Bottom"; and segments of Spinal Tap appearing on The Joe Franklin Show.

In the episode, Flekman is now a record label producer for The Brian Setzer Orchestra, and an ex-business partner of character Maxwell Sheffield (Charles Shaughnessy).

[61] A biographical comic book was released in 2018, That Was Spinal Tap, telling both the fictional story of the band and the real-life tale of the actors and others who created the characters and music.

In May 2022, director Rob Reiner announced that he is working on a sequel to the film, which will include him returning to play DiBergi, and McKean, Shearer, and Guest as the members of Spinal Tap.