In a year filled with several significant 50th anniversaries ~ of the Moon Landing, of the Woodstock music festival, of the Beatles' last performance, of the battle of Hamburger Hill in Vietnam, of the Stonewall riots in New York City ~ another one is the series of killings carried out by the Manson Family on August 8-9, 1969.
In Once Upon a Time in Hollywood, the relationship between actor Rick Dalton (Leonardo DiCaprio) and his stunt double/best friend Cliff Booth (Brad Pitt) is directly modeled on the friendship between Burt Reynolds and stuntman-turned-director Hal Needham, both of whom are now deceased.
Sharon Tate and the other targets of the Manson family -- Jay Sebring, Abigail Folger, and Wojciech Frykowski -- depicted here are obviously all real people, as were Manson himself and his followers Tex Watson, Susan Atkins, and Patricia Krenwinkel, and Linda Kasabian, the latter of whom became a cooperating witness at trial but is shown in the movie as fleeing before the crimes begin. (Ditto Dakota Fanning as Manson follower Squeaky Fromme.) Obviously, the fates of all the aforementioned people differ greatly in real life than what transpired in the film.
Unless you’re brand new to the planet Earth, yes, Bruce Lee was a real guy, the greatest martial artist-star of his time (arguably, of all time). Lee is depicted in the film, by Mike Moh, during his time starring as Kato on The Green Hornet. And, yes, he really did train Sharon Tate in karate when she was co-starring in the Dean Martin spy spoof The Wrecking Crew.
Homeland’s Damian Lewis plays Steve McQueen in one scene set at the Playboy Mansion. McQueen, like Rick Dalton, began as the star of a TV western about a bounty hunter — Wanted: Dead or Alive —before he became a movie star and pop culture icon thanks to films like The Magnificent Seven, Bullitt, and The Great Escape, which Rick fantasizes about starring in instead of McQueen at one point.
Timothy Olyphant and the late Luke Perry also play real people in the movie. Yes, Lancer was a real TV series and the actors they play — James Stacey and Wayne Maunder — were real. The last shot we see of Olyphant in the film, driving off on his motorcycle, is also a harbinger of the tragic fate that lay in store for Stacey (he lost two limbs and his girlfriend was killed in a motorcycle accident when they were hit by a drunk driver).
Also real? The TV series The FBI that Rick films a guest spot on as the bad guy of the week.
The Mamas and Papas’ Michelle Phillips and Mama Cass pop up during the Playboy Mansion scene.
With his silver mane and oversized glasses, Al Pacino's Marvin Schwarzs appears to be patterned after legendary Hollywood talent agent Lew Wasserman. Source.
Quentin Tarantino celebrates Hollywood with the people and the music, in many ways like Peyton Reed did with the technicolor of Hollywood in Down With Love.