One of the keys to a well-executed Biopic
or otherwise historical work is to successfully create the illusion of a period setting. In addition to details such as clothing, buldings and modes of speaking, another popular way to add context is to give appearances by famous real-life people of the period. These characters don't often have much to say or do, but add to the atmosphere of the movie, TV show, or novel nonetheless.
Compare Living Prop
and Historical-Domain Character
(when the work in question is mostly or entirely fictional). Can also cross over with Hey, It's That Guy!
if said famous person is played by another famous person
- The musical number "Paris Holds the Key To Your Heart" from Anastasia includes cameos from various famous people from 1920s Paris such as Sigmund Freud, Charles Lindberg, Claude Monet, Isadora Duncan and Josephine Baker.
- In The Aviator, Jude Law has a One-Scene Wonder appearance as Errol Flynn, and many of the famous females like Jean Harlow (Gwen Stefani), Ava Gardner (Kate Beckinsdale), and Faith Domergue (Kelli Garner) have similarly limited screen time (this is appropriate, as Howard Hughes treated them mostly as arm candy).
- The satiric Jack Abramoff biopic Casino Jack features appearances by Tom DeLay (though he is more a supporting character), Grover Norquist, Ralph Reed, Karl Rove, and even George W. Bush.
- Andy Warhol (played by Crispin Glover) shows up for a couple of minutes to chatter at the main characters of The Doors.
- Orson Welles (played by Vincent D'Onofrio) appears in Ed Wood in just one scene, but unlike most other examples of this trope, his appearance is quite significant to the plot.
- Harry S Truman appears in a single scene in Flags of Our Fathers to encourage the surviving members of the famous marine flag-raising photo they have to convince people to buy war bonds.
- Diane Sawyer appears briefly in Frost/Nixon as one of the co-writers of Richard Nixon's memoirs, and Neil Diamond performs at a nightclub where David Frost goes to for his birthday.
- In the surrealist Bob Dylan Biopic I'm Not There, most of the famous figures in Dylan's life (including Dylan himself) are represented through No Celebrities Were Harmed characters, with the strange exception of Allen Ginsberg, who shows up to give conversation to the Dylan expy played by Cate Blanchett.
- The Truman Capote Biopic Infamous features appearances by and quasi-documentary interviews with the likes of Harper Lee, Gore Vidal, Kitty Dean, Babe Paley, and Bennett Serf.
- Inglourious Basterds features brief appearances by the likes of Joeseph Goebbles and Emil Jannings, as well as a larger supporting role for Adolf Hitler.
- J. Edgar features a whole slew of these (though you may have to look fast to catch 'em all), including Bobby Kennedy, Charles Lindbergh, Richard Nixon, Dwight Eisenhower, Franklin Delano Roosevelt, Shirley Temple, Lucille Ball, and Ginger and Lela Rogers.
- Man on the Moon not only features appearances by the likes of David Letterman, Lorne Michaels, Jerry Lawler, the cast of Taxi and others, but most of them play themselves.
- Pretty Boy Floyd appears (played by Channing Tatum) in a brief, early scene in Public Enemies simply to be shot and killed by Melvis Purvis, thereby proving how much of a Bad Ass he is.
- Even contemporary-set films can feature this: Bill Gates appears as a guest lecturer at Harvard University in The Social Network.
- Parodied mercilessly in Walk Hard, where such musicians as Elvis Presley, Buddy Holly, The Big Bopper, Jerry Garcia, and The Beatles show up randomly during the course of the film, all with purposefully bizarre casting.
- The Opening montage of Watchmen has the famous kissing sailor & nurse from the end of WWII, Neil Armstrong, David Bowie as Ziggy Stardust, and various others, used to demonstrate the differences in a world with these costumed adventurers around: the female adventurer The Silhouette takes the sailor's place in the photo, Dr. Manhattan greets Armstrong on the moon, and Ozymandius & Ziggy have a Photo Op outside Studio 54.
- In the BBC America series, Copper, a recent addition to the cast is a certain actor by the name of John Wilkes Booth.
- The Young Indiana Jones Chronicles had Indy meeting all manner of famous personages in the early 20th century.
- The Kennedys miniseries does a fair amount of this. Obviously it's not unreasonable to suppose the Presidential family would meet lots of celebs.