Glass Onion: A Knives Out Mystery Featured a Well-Known Actor in a Surprising Role

Even with an all-star cast assembled for Glass Onion: A Knives Out Mystery, director Rian Johnson was still able to sneak in a surprising role for Joseph Gordon-Levitt. The new Knives Out brought back Daniel Craig as Detective Benoit Blanc to help solve another murder mystery, set on an island owned by a billionaire played by Ed Norton. One of the many extravagant displays of wealth on the island was an hourly dong, which would sound periodically throughout Glass Onion. Instead of the dong being a simple sound effect, Joseph Gordon-Levitt was recruited to be the "hourly dong."

In a "blink and you'll miss it" moment as the Glass Onion: A Knives Out Mystery credits are rolling, you can see Joseph Gordon-Levitt is credited as the "Hourly Dong." If you're curious how Gordon-Levitt wound up getting the under-the-radar role, it came down to already working with Rian Johnson on another Hollywood project.

Rian Johnson Explains Joseph Gordon-Levitt's Glass Onion Cameo

"He's in an episode of [Poker Face], this TV show I'm doing with Natasha Lyonne, Joe is the guest star of one of those episodes," Johnson told ET's Ash Crossan. "I just said, you have to trust me, say the word dong really loudly."

The director went on to give an explanation of what exactly the dong is.

"There's a thing on the island where every hour, you hear, 'Dong!' and it's the hourly dong, and goes off every hour," Johnson explained. "That's a reference to one of my favorite mystery movies, Evil Under the Sun, there's a big [plot point] in it with the 'noonday gun,' and they shoot a canon off at noon every day."

Of course, instead of a cannon, Glass Onion uses a dong. But Gordon-Levitt is also responsible for it being called an "hourly dong."

"In the script, it's written as, I think, the 'hourly gong,'" the director recalled. "One time, when everybody was saying it, [Joseph] said it wrong and said the 'hourly dong.' And I said, 'That's it, it's the hourly dong now.'"

When Will Knives Out 3 Be Released?

With many enjoying Glass Onion, the inevitable third Knives Out mystery may not be too far behind it. Glass Onion writer and director Rian Johnson, along with producer Ram Bergman, shared some insights about the Knives Out 3 process and timeline with

"Well, it's a good question," Bergman said when asked how long a third Knives Out movie will take to get made. "The first one, [Johnson] had the idea for years in his head, but he only put pen to paper like late January and by end of October we were filming it, which is a super fast. This movie, he really did not have an idea. He just stopped thinking and we were... From the moment he started really writing it, like, nine months later, a year later, we were filming. So, the good thing, he is very motivated to go do the next one as quickly as possible. But, you know, we'll see how fast he is but this is gonna be a challenge. It's gonna be a bigger challenge. So we'll see how long it's gonna take."