Inside Joseph Gordon-Levitt’s ‘Glass Onion’ Secret Cameo as ‘Hourly Dong’ (Exclusive)

Rian Johnson landed a truly star-studded cast for ‘Glass Onion: A Knives Out Mystery’ – but there’s one celeb you might have missed!

ET’s Ash Crossan sat down with the director to discuss Daniel Craig’s latest foray as Detective Benoit Blanc, but also got all the scoop on the film’s « hourly dong » jingle, which was voiced by none other than Joseph Gordon-Levitt.

« He’s in an episode of [“Poker Face”], this TV show that I’m doing with Natasha Lyonne, Joe is the guest star on one of those episodes, » Johnson said of the birth of the cameo. « I just said, you have to trust me, say the word dong real loud. »

ALSO: ‘Glass Onion’: Rian Johnson talks about working with Angela Lansbury and Stephen Sondheim on their latest film

So what is the hourly dong, exactly?

« There’s one thing on the island where every hour you hear, ‘Dong!’ and it’s the hourly dong, and it rings every hour, » Johnson explained. « It’s a reference to one of my favorite crime movies, ‘Evil Under the Sun’., there is a big [plot point] inside with the ‘fusil de midi’, and they fire a cannon at noon every day.

In « Glass Onion », however, instead of a cannon, it’s a « dong ». Only, it’s not quite what it was supposed to be, Johnson revealed.

« In the script, it’s written as, I think, the ‘hourly gong,' » he recalled. « Once, when everyone was saying it, [Joseph] said it wrong and said the ‘hourly dong’. And I said, ‘That’s it, it’s the hourly dong now.' »

The director also opened up about two more meaningful cameos that he said were « incredible » to cast – Angela Lansbury and Stephen Sondheim. The two just shared a small scene in « Glass Onion, » but that ended up being the last on-screen role for the two. Lansbury died in her sleep on October 11 at age 96, while Sondheim died at age 91 on November 26, 2021.

« I don’t want to blow it up too much, it’s just a fun little moment they’re having, » Johnson said of the scene. « But what it meant to me, besides how special it was to have both of them in the movie, it meant I just had to spend 10 minutes with each of them to capture that little moment. »

READ MORE: Kate Hudson and Kathryn Hahn on Their ‘How to Lose a Guy in 10 Days’ Reunion in ‘Glass Onion’ (Exclusive)

« Meeting them, telling Angela Lansbury what her job meant to me, talking to her about watching the film version of ‘Sweeney Todd’ that was on cable when I was a kid and how that really made me love musical theater … It felt like a very special privilege to be able to do that.

« Glass Onion: A Knives Out Mystery » is now streaming in limited theaters before premiering on Netflix on December 23.

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