Arianne Phillips is no stranger to designing iconic costumes. Going back to her 90s work on films like The Crow and Tank Girl, her glam-rock flourish in 2001's Hedwig and the Angry Inch, not to mention her long-running collaboration with Madonna, the two-time Oscar-nominated costume designer has an eye for creating looks that endure the test of time.

With Quentin Tarantino's Once Upon a Time in Hollywood, Phillips' first collaboration with Tarantino, she's done it again. Tarantino spared no expense or attention to detail when it came to turning back the clock for his 1969-set love letter to Los Angeles, and when it came time to costume his characters -- both beloved real-life movie stars of the era and newly created characters like Rick Dalton (Leonardo DiCaprio) and Cliff Booth (Brad Pitt) -- Tarantino turned to Phillips for the job. And if the amount of Ricks and Cliffs walking around at Halloween were any indication, she once again tapped into her knack for iconography in design.

With Once Upon a Time in Hollywood now on digital and arriving on Blu-ray and DVD later this month, I had the opportunity to join a group of journalists (at the film's key throwback setting of Musso & Frank Grill no less) to chat with Phillips about creating the film's costumes. Phillips had plenty to say about crafting the looks with Tarantino and broke down all the incredible design details you probably missed.

Why are the details so key, even if you don't always notice them on screen? Phillips explained, "The details are always really important to me in the costume. They help create layers in the character and they also help, I hope, assist the actor in becoming that character."

With that character-first approach in mind, Phillips set out to create "talismans" for each character, something small and specific that spoke to their individual personalities -- specific costuming details that helped tap into the essence of that character. As Phillips explained, it was up to the actors and Tarantino if they wanted to embrace those, but as it turned out, DiCaprio, Pitt and Margot Robbie all took to the designs she laid out.

For Rick, that talisman was a medallion necklace, modeled after the "bad boys" of the era, a la Steve McQueen (who also appears in the film, played by Damian Lewis.) Jumping from that inspiration, Phillips designed an original medallion -- a Tudor Rose-inspired pattern on one side, and a monogrammed "R" on the other. And if that wasn't enough movie star machismo for you, Rick's belt buckle is also monogrammed with an "R". "The person who has monogrammed clothes has a bit of an ego, a bit of bravado, so I loved that Rick," she explained. However,  Philips and her team made sure that whenever Rick was wearing that belt, the necklace was turned around to the Tudor pattern. Turns out two monograms is too much, even for someone like Rick Dalton.

As for Cliff, Phillips settled on his Stuntmen's Association belt buckle, something she discovered while going through boxes of thousands of belt buckles in what she describes as a "Eureka!" moment for his costume. Phillips tracked down one that was dated in the 60s so she knew that they were being manufactured in the time period of the film, and presto, Cliff had a talisman all his own.

But he also had one of the most instantly iconic Hawaiian T-shirts in Tarantino's proud history of Hawaiian T-shirts and it was up to Phillips to design, what might seem on the surface, like one of the easiest pieces in the film. But Phillips explained that, while she took inspiration from vintage pieces, those were ultimately used for the hundreds of background actors she and her team had to dress. The costumes for the principals were all handmade. And that includes the Hawaiian shirt.

"In Quentin’s script, it was scripted that Cliff Booth wears a Hawaiian shirt. Now, Hawaiian shirts are kind of part of the Quentin Tarantino vernacular, we’ve seen them before in other iterations of his films, so I knew that this needed to be unique to Once Upon a Time in Hollywood," Phillips said.

"I looked at every imaginable vintage Hawaiian shirt you can imagine and, in the end, I was inspired to make this shirt, which is based on a similar vintage shirt that I had seen, but we changed the pattern to be not a Hawaiian motif, but an Asian motif with the Hawaiian shirt cut, just to keep it in its own world." As for that brilliant yellow color, Phillips explained, "I used a lot of yellow in this film. For me, yellow really represents California, it's a color that was very commonly used in the 60s," she continued. "And it looked good particularly on Brad Pitt."

Lest we forget the characters' shoes, which say a surprising amount about their identities. "I read a quote when I was a young person where Laurence Oliver said he always started with his character from the shoes up. We all know what it’s like to wear a pair of shoes that make us feel good and strong and we also know what it’s like to wear a pair of shoes that make you feel not safe or not yourself. I took that to heart," Phillips said. "For a costume, I feel like a character starts with the shoes and that’s how you get the balance of the silhouette."

"You can really tell the difference between Cliff Booth and Rick Dalton by their shoes," she explained. "Rick Dalton wears cowboy boots, right? He wears cowboy boots when he’s not working and he wears them because they’re cool and they give him — If you imagine the feeling of wearing cowboy boots it makes you feel like a badass, right? Tough, strong, protected. And it’s a pair of boots he probably would have worn on Bounty Law or Lancer, so it’s a part of his persona." In fact, Phillips noted that Tarantino had a particularly comic idea about Rick's costumes. "Quentin had a lot of ideas about his day wear as Rick Dalton, that maybe he took them off the wardrobe people from the set because he was too lazy to buy himself clothes."

And what's more different from a cowboy boot than a moccasin? "Cliff Booth, on the other hand, we were really quite inspired by the Tom Laughlin character Billy Jack, which is this kind of denim-on-denim thing, and the idea of him wearing moccasins was just badass. In a different way," Phillips said.

The moccasins weren't just a fashion choice, they were indicative of the character. "It’s total confidence to wear a soft shoe like that. If you think about the scene with him and Bruce Lee, knowing how confident he was and what a badass, and of course there’s this terrible rumor that he killed his wife. So I felt there was a dangerousness in wearing moccasins," Phillips said. "It’s the opposite of what you think of. He doesn’t have to prove to anyone he’s a tough guy. He’s a stunt man, he throws himself off buildings. So I loved the vulnerability that it could be like and the strength it would take for a person to wear moccasins." 

But yes, it was a bit of a fashion choice too. Phillips explained, "It's another hint that Clint knows what’s going on. Moccasins were something that the hippies were wearing, young people were wearing, and it also goes to his silhouette of being casual and being comfortable in his clothes."

And then, of course, there's Sharon Tate, the real-life movie star who was horribly murdered by the Manson cult, and who features as a central character in Tarantino's alt-history film. Phillips explained that Tate's sister, who has been famously protective of her sister's image and legacy in the years since her death, not only gave her blessing to Once Upon a Time in Hollywood, she let them have access to Sharon Tate's old jewelry. For Robbie and Phillip's costume design, that became a powerful indicator and reminder of the real woman beyond the tragedy.

"We had the great good fortune of having Deborah Tate, Sharon’s sister as a consultant on our film and Deborah was generous enough to show me some of Sharon’s clothes, some of her jewelry, her sunglasses. Just to be able to touch and feel — there’s an osmosis, I think," Phillips said. "There’s a reverence and a responsibility I felt as a costume designer in recreating who Sharon Tate was and, luckily, to be able to have anecdotes and stories from her sister about who she was, was really important for me."

Phillips asked if they could use some of those pieces for the film, and checked in with Robbie and Tarantino about how they felt, and ultimately, those pieces became a throughline of the character's design. "Basically in the whole film, she’s wearing a ring or an earring that belonged to the real Sharon Tate. So details like that might really inform the actor and act as a kind of “beam me up” suit to help access a character," Phillips said. "I believe that responsibility as a costume designer is just as important as all the visual clues that costumes serve for the audience."

Once Upon a Time in Hollywood is now available on digital. For more on the film, be sure to check out how the film is stacking up in the Best Picture Oscar race.