“Once Upon a Time in Hollywood,” the latest film from Quentin Tarantino, stars Margot Robbie, Brad Pitt, and Leonardo DiCaprio, and is one of the director’s most ambitious films to date.

Shrouded in secrecy since its inception, “Once Upon a Time in Hollywood” tells the story of aging Western actor Rick Dalton, played by DiCaprio, and his friend/stunt double Cliff Booth, played by Pitt.

The film is set in Hollywood, 1969, and juxtaposes Dalton and Booth’s friendship with the growing threat of the Manson family -the group of hippies and eventual murderers who killed actress Sharon Tate, played by Margot Robbie, and several others in August of that year.

Since its release last month, Tarantino has made headlines for not permitting the use of cell phones on set. It was also revealed that only one complete copy of the script was in existence, and kept in a safe in the director’s home to prevent a leak, similar to what occurred with Tarantino’s 2015 film “The Hateful Eight.”

Here are eight things you didn't know about the making of "Once Upon a Time in Hollywood."

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Foto: Leonardo DiCaprio stars in "Once Upon a Time in Hollywood."sourceSony Pictures

Tarantino didn't allow cell phones on set and would fire anyone who used it to text or call during filming.

Timothy Olyphant, who plays Dalton's "Lancer" costar James Stacy, told Rich Eisen's radio show that Tarantino didn't allow any cell phones on set.

"Quentin's got no cellphones allowed on set," Olyphant said. "None. You're fired. Cellphone out? Done. No warning, nothing, you're going home."

"I'm not telling tales," he added.

Olyphant shared that there were phone booths outside on the street where cast and crew members could make phone calls if needed.

"If you needed to make a phone call, you go out onto the street and you make a phone call," he said.

Read more: 'Once Upon a Time in Hollywood' actor Timothy Olyphant says Quentin Tarantino will fire anyone who uses a phone on set

Even though Tarantino took extra precautions to ensure the script and/or plot of the film wasn't leaked before its release, Olyphant thought the no-phones policy had more to do with creating a distraction-free atmosphere.

"I think it's about creating an environment where, while we're all here, making this thing, that's what we're all going to do," he said.

"We're not going to be over there doing some other thing, Instagramming, or working on your next script, or talking to your agent," he added. "No. We're here, and this is what we're doing."

Only one complete copy of the script for 'Once Upon a Time in Hollywood' existed - and Tarantino kept it in a locked safe

Tarantino had complete control over the final version of the script, and kept the sole copy in a locked safe -meaning that cast and crew members who needed to read it had to do so either in Tarantino's home or his office, often with the director still in the room, according to interviews with Robbie, Pitt, and DiCaprio.

The secretive move comes after the scripts for Tarantino's last three films (2009's "Inglourious Basterds," 2012's "Django Unchained," and 2015's "The Hateful Eight") were leaked before their respective releases.

Every person who read the script had to sign a nondisclosure agreement, and only Robbie, DiCaprio, and Pitt knew about the film's revisionist ending, per the Huffington Post.

The reports that DiCaprio had a 'no eye contact' rule on set are false

An article from the Hollywood Reporter last month said certain members of the film crew were instructed to not make eye contact with DiCaprio on set, but the film's production designer Barbara Ling said that's not true.

"[DiCaprio is] the sweetest," Ling told the Huffington Post.

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Foto: Margot Robbie plays murdered actress Sharon Tate in the film.sourceSony Pictures

Margot Robbie wore some of Sharon Tate's real jewelry in the film

In an interview with "E! News," Robbie revealed that she wore some of Tate's jewelry in the film, and even spoke with the deceased actress' sister, Debra.

"Wearing some of the pieces of her jewelry and spending time with her sister definitely made me feel closer to her in a way that I don't think I could have with just reading things and watching things [about her life]," Robbie said.

"Having that more personal connection meant a lot to me," she added.

Tate is portrayed in the film by Robbie and was murdered in August 1969 by members of the Manson family. She was eight months pregnant at the time of her death - but "Once Upon a Time in Hollywood" takes a very different approach to Tate's murder and the fate of the Manson family.

Brad Pitt let a pitbull lick baby food off his neck for a scene

One of the undisputed stars of "Once Upon a Time in Hollywood" is Cliff Booth's pit bull, called Brandy in the film.

During a recent interview, Pitt, who plays Cliff, revealed that he had to put baby food on his neck in order to get the dog to lick his neck during one scene.

Read more: Brad Pitt says he put baby food on his face so a pitbull would lick it during a scene in 'Once Upon a Time in Hollywood'

"I equated it to, Tom Cruise chained himself to the side of a plane and it took off and landed, and then I put baby food on my neck and let a pitbull have at it," the actor joked when asked if he "suffered" for his art.

In addition to being an adorable companion for Pitt's character Cliff, the pitbull, called Brandy in the film, also ends up being a key part of the climax of "Once Upon a Time in Hollywood."

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Foto: Cliff Booth, played by Brad Pitt, is a dedicated owner to Brandy the pitbull in "Once Upon a Time in Hollywood."sourceSony Pictures

Tarantino created the brand of dog food that Cliff Booth's pitbull, Brandy, eats in the film

Much like Red Apple cigarettes and Big Kahuna burgers, the brand of dog food that Cliff feeds Brandy in the film was created by Tarantino.

In one of the more heartwarming sequences in "Once Upon a Time in Hollywood," Cliff returns home to his trailer, and feeds Brandy a feast of "Wolf's Tooth" dog food, a made-up brand that features exotic flavors like rat, raccoon, and lizard.

The slogan for Tarantino's brand is "Good Food for Mean Dogs" - a bit misleading, considering Brandy is such a good girl for most of the film.

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Foto: Brandy is played by several pit bulls in "Once Upon a Time in Hollywood."sourceSony Pictures

Brandy was actually played by three different pit bulls, all of whom bonded with Pitt before each day of filming

Even though only one pup (named Sayuri) is credited with playing Brandy, the Huffington Post revealed that it was actually three dogs who portrayed Cliff's loyal companion - two females and a "more aggressive" male dog for the film's graphically violent finale.

Since chemistry between a dog and its owner, fictional or otherwise, are key, Pitt needed to spend time with the dogs before filming, to ensure that their bond seemed real and that the dogs were able to follow his commands safely.

Handlers would bring the pitbulls to set early each day so that Pitt would get a chance to play and cuddle with them before the day's filming began.

"He would always go up to them and feed them or touch them so he could keep that bond going knowing that the scene was about to play," longtime cinematographer Robert Richardson said to the Huffington Post.

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Foto: Brad Pitt and Mike Moh did their own stunts for "Once Upon a Time in Hollywood."sourceSony Pictures

The scene where Pitt fights with Mike Moh, who plays Bruce Lee, featured both actors doing their own stunts

Co-stunt coordinator Robert Alonzo said that he spent several months training Pitt and Moh, who plays iconic martial artist Bruce Lee, for their fight scene in the film. The actors even perform their own stunts in the film, which means that every part of the fight scene - including the part where Moh appears to be thrown against a car - is really them.

"I've done so many movies with Tom Cruise that I know how to get people to do their own stunts," Alonzo told the Huffington Post.