Once Upon A Time In... Hollywood is a story of dreams of making it big, grappling with stardom, and murder, but just like the industry in which it's set, there is quite a bit of movie magic mixed in with the true story. In this case, it's the true stories that have been mixed in to add some sunshine-hued color to the world of the movie's fictional leading men. So no, sorry, Leo DiCaprio's Rick Dalton isn't a real person.
Though Once Upon A Time In... Hollywood portrays a real, but often unseen, side of Hollywood, the film is largely fictional and set against the backdrop of real events that transpired during the height of the free love movement. Real celebrities of the time – such as Bruce Lee, Sharon Tate, and Steve McQueen – and real-life tragedies like the Manson family murders lend a sense of reality to the thematically chaptered Tarantino film.
DiCaprio plays Rick Dalton, a struggling actor fighting his way up the ladder from a career in television to the much more lucrative role of big time movie star. But just like the movies Dalton stars in, his character takes a lot of inspiration from big name actors from the time period.
Once Upon A Time In... Hollywood director Quentin Tarantino spoke at length on Pure Cinema Podcast about how he sourced inspiration for DiCaprio and Brad Pitt's characters. Dalton is not unlike Steve McQueen who went from TV to film in the 1960s. "He really wants to get rid of this TV series, so he can go on to his greater fortune in movies," said Tarantino, offering some background on DiCaprio's character. "So, he does and gets a four-picture deal at Universal. And he makes four movies there. They're not bad, but nothing really knocks anybody out. And so, he doesn't pull off the TV-to-movies transition."
The same fate was not true for his real-life inspiration, McQueen, who went on to be nominated for multiple Golden Globes and eventually become executive producer on many of his later films.
In fact, McQueen had his own connection to the Manson murders. He may not have lived next door to Sharon Tate like DiCaprio's character does in the film, but McQueen was invited to the fateful house party at Tate's Hollywood home. Had he not had other plans, he could have suffered the same fate as Tate and her guests.
Dalton may not be real, but just like everything in Hollywood, there is always a small piece of truth in every work of fiction.