In the midst of yet another wave of rave reviews, Once Upon a Time... in Hollywood took over—where else?—Hollywood for its Los Angeles premiere on Monday night. And, as you might expect given its debut at the Cannes Film Festival in May, which just might be the biggest red carpet of the year, the cast and crew of Quentin Tarantino's latest pulled out all the stops. The evening also served as a reminder of who's actually part of the massive cast—aside from Leonardo DiCaprio, Brad Pitt, and Margot Robbie, of course. Maya Hawke, Margaret Qualley, Sydney Sweeney, and Timothy Olyphant were just some of those in attendance, easily making up for the absence of Lena Dunham, Al Pacino, Dakota Fanning, and several other costars.

And yet, the celebs who managed stand out amidst all the star power weren't even a part of the film's cast. None other than Britney Spears not only made an unexpected appearance, but also finally made her red carpet debut with Sam Asghari, whom she's been dating since 2016, after they met on the set of one of her music videos.

Britney Spears and Sam Asghari on the red carpet of the Los Angeles premiere of Once Upon a Time ... in Hollywood in Hollywood on July 22, 2019.

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Asghari has joined Spears at photographer-heavy events before, like last year's GLAAD Media Awards, but this time, he didn't skip the red carpet. (Though he did keep things low-key in a beige suit.) Spears, on the other hand, looked radiant in a bright red dress—plus a diamond ring that almost immediately prompted speculation that she and Asghari are engaged. For what it's worth, Asghari refrained from calling Spears his fiancée on either of their Instagrams; he commented "my beautiful date" on the pre-red carpet photo that Spears posted, and referred to her as "the lioness" in his own Instagram caption.

Spears and Asghari may have stolen the spotlight, but they were far from the only couple to turn the premiere into a date night. Behold:

Austin Butler and Vanessa Hudgens

Vanessa Hudgens and Austin Butler on the red carpet of the Los Angeles premiere of Once Upon a Time ... in Hollywood in Hollywood on July 22, 2019.

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Thanks to the announcement of his starring role as Elvis Presley in Baz Luhrmann's upcoming biopic, Austin Butler—who reportedly beat out Ansel Elgort and Harry Styles for the part—drew more eyes than usual on the red carpet. The 27-year-old actor was dressed head-to-toe in black, as was his girlfriend of eight years, Vanessa Hudgens.

Chris Hemsworth and Elsa Pataky

Elsa Pataky and Chris Hemsworth on the red carpet of the Los Angeles premiere of Once Upon a Time ... in Hollywood in Hollywood on July 22, 2019.

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Chris Hemsworth might not have joined his A-list colleagues on-screen, but he did do so on the red carpet, along with his wife, Elsa Pataky. In fact, the Hemsworth clan had quite a presence on the red carpet: Luke and Samantha Hemsworth were also on hand. (Though the other Hemsworth brother, Liam, and his wife, Miley Cyrus, took a pass.)

Sofia Vergara and Joe Manganiello

Joe Manganiello and Sofia Vergara on the red carpet of the Los Angeles premiere of Once Upon a Time ... in Hollywood in Hollywood on July 22, 2019.

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Is Sofia Vergara part of the illustrious cast of Once Upon a Time—or, for that matter, her actor husband Joe Manganiello? Nope—and nope. But they seem to have enjoyed their night with the film's actual stars all the same.

Robin Thicke and April Love Geary

April Love Geary and Robin Thicke on the red carpet of the Los Angeles premiere of Once Upon a Time ... in Hollywood in Hollywood on July 22, 2019.

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The same goes for the singer Robin Thicke and the model April Love Geary, who braved the spotlight less than a month after causing a minor scandal by Instagramming a video of their 16-month-old daughter snacking on Flamin' Hot Cheetos. As for why they were in attendance, that might have something to do with the fact that they've begun cozying up to Leonardo DiCaprio. The pair recently celebrated Thicke's 42nd birthday together and also faced off in a volleyball match with their girlfriends. (Coincidentally, both women are about two decades younger than their famous beaus.) Speaking of DiCaprio...

Leonardo DiCaprio and Brad Pitt

Brad Pitt and Leonardo DiCaprio on the red carpet of the Los Angeles premiere of Once Upon a Time ... in Hollywood in Hollywood on July 22, 2019.

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With no hint of his girlfriend Camila Morrone in sight, Leo found another date in a 55-year-old actor: Brad Pitt. After all, while Once Upon a Time ostensibly focuses on the Manson murders, it's really all about Brad and Leo, who've recently turned their on-screen bromance into an IRL love fest. According to the tabloids, they've recently taken up making pottery and eating sandwiches together. Cute!!

Related: The Once Upon a Time Crew Reportedly Went to Great Lengths to Protect Leonardo DiCaprio's Eyes