1970s Guest began his career in theatre during the early 1970s with one of his earliest professional performances being the role of Norman in
Michael Weller's
Moonchildren for the play's American premiere at the
Arena Stage in Washington, DC, in November 1971. Guest continued with the production when it moved to
Broadway in 1972. The following year, he began making contributions to
The National Lampoon Radio Hour for a variety of National Lampoon audio recordings. He both performed comic characters (Flash Bazbo—Space Explorer, Mr. Rogers, music critic Roger de Swans, and sleazy record company rep Ron Fields) and wrote, arranged, and performed numerous musical parodies (of Bob Dylan, James Taylor, and others). He was featured alongside
Chevy Chase and
John Belushi in the
off-Broadway revue ''
National Lampoon's Lemmings. Two of his earliest film roles were small parts as uniformed police officers in the 1972 film The Hot Rock'' and 1974's
Death Wish. Along with
Bill Murray,
Brian Doyle-Murray, and others, Guest was one of the "Prime Time Players" on
Saturday Night Live with Howard Cosell. This was the short-lived variety show that aired from September 20, 1975, to January 17, 1976, not to be confused with the long-running sketch show
Saturday Night Live, which began airing a month later and lampooned the group by billing their own sketch comedy actors as "The Not Ready for Prime Time Players". Guest played a small role in the 1977
All in the Family episode "
Mike and Gloria Meet", where in a
flashback sequence Mike and Gloria recall their first blind date, set up by Michael's college buddy Jim (Guest), who dated Gloria's girlfriend Debbie (
Priscilla Lopez). Guest also had a small but important role in
It Happened One Christmas, the 1977 gender-reversed TV remake of the Frank Capra classic ''
It's a Wonderful Life,'' starring
Marlo Thomas as Mary Bailey (the Jimmy Stewart role), with
Cloris Leachman as Mary's guardian angel and
Orson Welles as the villainous Mr. Potter. Guest played Mary's brother Harry, who returned from the Army in the final scene, speaking one of the last lines of the film: "A toast! To my big sister Mary, the richest person in town!"
1980s Guest's biggest role of the first two decades of his career is likely that of
Nigel Tufnel in the 1984 Rob Reiner film
This Is Spinal Tap. Guest made his first appearance as Tufnel on the 1978 sketch comedy program
The TV Show. Along with
Martin Short,
Billy Crystal, and
Harry Shearer, Guest was hired as a one-year-only cast member for the
1984–1985 season on
NBC's
Saturday Night Live. Together, Guest, his frequent writing partner
Eugene Levy, and a small band of actors have formed a loose
repertory group, which appears in several films. These include
Catherine O'Hara,
Michael McKean,
Parker Posey,
Bob Balaban,
Jane Lynch,
John Michael Higgins,
Harry Shearer,
Jennifer Coolidge,
Ed Begley Jr.,
Jim Piddock and
Fred Willard. Guest and Levy write backgrounds for each of the characters and notecards for each specific scene, outlining the plot, and then leave it up to the actors to improvise the dialogue, which is supposed to result in a much more natural conversation than scripted dialogue would. Typically, everyone who appears in these movies receives the same fee and the same portion of profits. Among the films performed in this manner, which have been written and directed by Guest, include
Waiting for Guffman (1996), about a
community theatre group,
Best in Show (2000), about the
dog show circuit,
A Mighty Wind (2003), about
folk singers,
For Your Consideration (2006), about the hype surrounding
Oscar season, and
Mascots (2016), about a sports team
mascot competition. Guest had a guest voice-over role in the animated comedy series
SpongeBob SquarePants as SpongeBob's cousin, Stanley. Guest again collaborated with Reiner in
A Few Good Men (1992), appearing as Dr. Stone. In the 2000s, Guest appeared in the 2005 biographical musical
Mrs Henderson Presents and in the 2009 comedy
The Invention of Lying. He is also a member of the musical group
The Beyman Bros, which he formed with childhood friend
David Nichtern and Spinal Tap's keyboardist C. J. Vanston. Their debut album
Memories of Summer as a Child was released on January 20, 2009. In 2010, the
United States Census Bureau paid $2.5 million to have a television commercial directed by Guest shown during television coverage of
Super Bowl XLIV. Guest holds an honorary doctorate from and is a member of the board of trustees for
Berklee College of Music in Boston. In 2013, Guest was the co-writer and producer of the
HBO series
Family Tree, in collaboration with
Jim Piddock, a story in the style he made famous in
This is Spinal Tap, in which the main character, Tom Chadwick, inherits a box of curios from his great-aunt, spurring interest in his ancestry. On August 11, 2015,
Netflix announced that
Mascots, a film directed by Guest and co-written with Jim Piddock, about the competition for the World Mascot Association championship's Gold Fluffy Award, would debut in 2016. Guest was offered an opportunity to do another film for Netflix, but, by his own account, didn't have an idea for one and essentially decided to retire instead. He did reprise his role as Count Tyrone Rugen at a table read in the
Princess Bride Reunion on September 13, 2020. After a nine-year absence from film acting, Guest came out of retirement in 2025 to reprise the role of Nigel Tufnel in
Spinal Tap II: The End Continues. == Family ==