Real Person Cameo

In Biopics and dramatizations of true events where the principal figure, though portrayed in the show by some Hollywood star, is still alive in Real Life, it's a traditional Casting Gag to assign this non-actor some bit part (not As Himself).

A subtrope of The Cameo. Compare Celebrity Paradox, Autobiographical Role. Supertrope of Reciprocal Real Person Cameo.

Examples of Real Person Cameo include:

Comic Books

Dan Choi, known for his activism in the effort to repeal the Don't Ask, Don't Tell policy, appears in issue #4 of Batwoman's run in Detective Comics. He is attending West Point with Kate Kane and speaks to her just before she is outed and "separated" from the military. He was consulted for the story in that issue and receives "special thanks to 1LT Daniel Choi (USMA 2003) for his generous assistance in research for this issue" on the cover page.

Films

The 1948 Franco-Norwegian film Kampen om tungtvannet (The battle for heavy water) with Jens-Anton Poulsson, Claus Helberg Urbye, Thorstein Skinnarland and HH Halban as themselves.
Cleverly used in Erin Brockovich. When Erin is in a restaurant, one of the waitresses is being played by the real Erin Brockovich. She even has a nametag that reads "Julia", as Brockovich is played by Julia Roberts.
- And at the table behind her is the real Ed Masry, the lawyer who represented Erin.
The film adaptation of The Right Stuff had a couple of NACA recruiters visiting Pancho's Happy Bottom Riding Club outside of Edwards AFB, sizing up the test pilots present. The old man who interrupts them to ask if they want any whiskey is the real Chuck Yeager, whom they were discussing.
The real Baroness Maria von Trapp along with her daughter and granddaughter appears briefly as extras in the movie version of The Sound of Music.
- They are in the background during the song, "I Have Confidence", at the line, "I must stop these doubts, all these worries/If I don't, I just know I'll turn back."
In The Pursuit of Happyness, the real Chris Gardner (Will Smith's character) is the very well-dressed black man crossing the street behind Will Smith and his son at the end of the movie.
Jim Garrison played Earl Warren in JFK (Kevin Costner played Garrison).
In The People vs. Larry Flynt, Woody Harrelson, playing Flynt, has a really nasty judge hearing one of his obscenity trials. The judge is played by Larry Flynt.
Apollo 13 features a cameo by astronaut Jim Lovell (who flew on the actual Apollo 13 mission) as the captain of the aircraft carrier that recovers the crew after splashdown. Lovell is, of course, being played by Tom Hanks. The cameo is doubly appropriate, given that Lovell is a retired navy Captain.
- The plan was for him to be an admiral for the part, but he declared 'I retired a captain, and I'll be a captain.'
The real Frank Abagnale Jr. was an extra in Catch Me If You Can. He played one of the French police officers.
Tony Wilson himself appears as a TV studio technician in 24 Hour Party People. After his cameo, it is immediately pointed out by the actor playing Tony Wilson (the film has No Fourth Wall, at least when dealing with the main character) who then also mentions several other cameos by actual musicians from throughout the film to that point. One notable example features Howard Devoto, the lead singer for the bands The Buzzcocks and Magazine, appearing in a scene featuring the actor playing him, only to turn around and bluntly state that he doesn't remember this happening at all. It's that kind of Biopic.
In Fear and Loathing in Las Vegas, Hunter S. Thompson's alter ego Raoul Duke (played by Johnny Depp) has a flashback in a nightclub where he hallucinates that he sees himself sitting at a table. The man at the table is the real Hunter S. Thompson.

"There I was... holy shit, there I am!

In the film In The Mood, about a boy who has affairs with two much older women back when it wasn't cool to do that sort of thing (at least publicly), Ellsworth Wisecarver, the boy who had the affairs with the women in 1944, plays a man who accuses the boy of being a communist during a TV interview.
Spike Milligan plays his own father in the film version of Adolf Hitler: My Part in his Downfall.
Milk has the real Cleve Jones as Don Amador.
At the end of Schindler's List, the actors portraying the major characters walk hand-in-hand with the people they portrayed, placing stones on Schindler's grave.
Alice Brock, the "Alice" in "Alice's Restaurant" (remember Alice? It's a song about Alice), has a cameo in the movie adaptation of the song.
Ryan White had a small part in The Ryan White Story as another boy with AIDS.
In Falling from the Sky: Flight 174, when two guys just out of a flight simulator complain to an examiner that it's impossible for both engines to fail because of a pump failure, the examiner tells them that this exact scenario has actually happened. The examiner is played by Robert Pearson, the Captain of The Gimli Glider, a Boeing 767 which ran out of fuel in midair.
Some Came Running is a 1958 film starring Frank Sinatra and Dean Martin, in which a number of poker games are portrayed. In one such game, Frank and Dino are playing against James Jones, who wrote the novel upon which the movie is based. (For you ultimate trivia buffs, another person at the same table is Uncle Leo.)
David Fincher 's 2007 movie Zodiac features a brief appearance of Zodiac survivor Bryan C. Heartnell. Heartnell also consulted for the film.
Author J. G. Ballard cameos as a party guest in Empire of the Sun, adapted from his semi-autobiographical novel of the same name.
The Man Who Never Was featured Ewen Montagu, who wrote the book, playing a senior officer who expresses skepticism about Montagu's plan. They had to reshoot the scene several times because actor Clifton Webb, playing Montagu, kept breaking up laughing.
Man On The Moon features a number of these - for example, the real Bob Zmuda (played by Paul Giamatti in the film) appears as the producer of ABC's "Fridays."
George Harrison, one of the biggest supporters of The Rutles, appears in the film as a grey-wigged reporter.
Aside from being portrayed by an actor as part of the Rolling Stone staff, the actual Jann Wenner has a cameo in Almost Famous, reading a newspaper in the back of a taxi.
The French Connection has appearances by Eddie "Popeye" Egan and Sonny "Cloudy" Grosso, real-life NYC cops and the inspirations for the movie's Jimmy "Popeye" Doyle and Buddy "Cloudy" Russo.
In Casino, Frank Cullotta, the inspiration for Frank Vincent's character, appears at the end of the film as a hit man dispatched to eliminate those who have outlived their usefulness.

Live-Action TV

In Toast, The BBC's dramatisation of celebrity chef Nigel Slater's autobiography, Slater plays the chef who gives young Nigel his first job.
Happens more than once on The Wire, as several characters are loosely based on real cops and criminals who are given cameos on the show. Most notably, the real Jay Landsman ends up playing a recurring character.
Sue Thomas appears in three episodes of Sue Thomas: F.B.Eye. In two of them, she plays a character called Deanne Bray!
In Micro Men Sophie (née Roger) Wilson, as well as being a major character played by actor Stefan Butler, has a cameo right at the end of the programme as a pub landlady.

Web Original

In Funny or Die's spoof trailer for Weird: The Al Yankovic Story, the faux Al's goatee'd manager is played by Al himself.