Joseph Gordon-Levitt! Serena Williams! Glass Onion Casting Directors Break Down the Movie's Cameos

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The question for Benoit Blanc, the intrepid detective Daniel Craig plays in the Netflix murder mystery Glass Onion: A Knives Out Mystery, is "Whodunit?"

The question for viewers is, "Wait, was that just…?"

Writer-director Rian Johnson packed the movie—about eccentric billionaire Miles Bron (Edward Norton) who invites his frenemies to a private Greek island for a dinner party that turns deadly—with several cameos. That's in addition to the A-list main cast, which includes Craig, Norton, Kate Hudson as a self-involved model-designer, Janelle Monáe in a star turn as Bron's bitter former business partner, and Kathryn Hahn as the governor of Connecticut.

"It was just really important that they all fit together the right way," casting director Mary Vernieu tells PEOPLE of assembling the group. "It's a puzzle."

Vernieu and her colleague Bret Howe (they both worked on the original 2019 Knives Out, too) break down the big names.

Angela Lansbury, Stephen Sondheim, Kareem Abdul-Jabbar & Natasha Lyonne

Before jetting off to Greece, Blanc is seen at home playing the computer mystery game Among Us with Lansbury, who died in October at 96; Sondheim, who passed in 2021 at 91; Abdul-Jabbar, 75, and Lyonne, 43, appearing as themselves virtually on Blanc's laptop screen.

"They all have a relationship to mystery in one way or another," says Vernieu. Indeed, Lansbury headlined Murder, She Wrote, composer Sondheim was a huge fan of the genre, basketball legend Jabbar has written novels about Sherlock Holmes, and Lyonne stars in Johnson's upcoming Peacock detective series Poker Face, which is "like a throwback to Columbo," adds Vernieu.

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Hugh Grant

In a blink-and-you'll miss it scene, the rom-com mainstay, 62, answers the door to Blanc's apartment, revealing his character, Phillip, to be the detective's romantic partner. Vernieu says a few actors' names were bandied about, but Grant was at the top of Johnson's list.

Yo-Yo Ma

Johnson wrote the 19-time Grammy-winning cellist, 67, into the script for a scene in which he plays a party guest who helps model-designer Birdie (Hudson) open her puzzle-like invitation from Bron. "It was definitely a unique process, getting in touch with his people and finding him," says Howe. Once he and Vernieu did, Howe says the musician "was all in."

Ethan Hawke

When Bron's guests assemble on a dock to be taken to his island, the Efficient Man, as Hawke's character is credited, appears briefly to seemingly vaccinate the group. Hawke, 52, was able to shoot the scene because he was filming Moon Knight in nearby Hungary and was free to come to Greece for a day.

"The role was written in, but it wasn't written in as [Hawke]," says Vernieu. Filming occurred "at the height of the pandemic," she continues, "So we were really grateful that Ethan was able to work it out."

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Joseph Gordon-Levitt

Heard but not seen, the actor, 41—who has collaborated with Johnson on movies like Brick and Looper— provides the sound of the hourly gong on Bron's island. "That's Rian's thing," says Howe. "Joe is in everything he does in some fashion."

RELATED:  Everything to Know About Netflix's Glass Onion: A Knives Out Mystery

Serena Williams

At first glance, Williams seems to be a poster hanging on the wall of Bron's gym. But slowly, the tennis ace, 41, begins to move. "You're like, "What? She's in there!" says Vernieu of the clever way Williams, playing herself, is introduced.

Turns out, in the Glass Onion world, Williams is available for virtual work-outs via a Mirror-like fitness app at Bron's home gym. In the scene, she offers Blanc a sweat session, but he's too knee-deep in detective work with Monáe's character to oblige.

Landing Williams was particularly sweet, says Vernieu, because Johnson "has always been a huge fan." In the end, she says, the writer-director "got everyone he wanted."

Glass Onion: A Knives Out Mystery is now streaming on Netflix.