Joker: Every Easter Egg & Reference We Spotted

7. Cameo: Justin Theroux

Perhaps even more subtle than Todd Phillips' cameo is the squint-or-you'll-miss-it appearance by actor Justin Theroux.

When Arthur is practising at home for his gig on Franklin's TV show, he performs in sync with a recording of the show, where Franklin introduces a guest named Ethan Chase, said to be the star of a fictional movie called American Playboy.

We only catch a briefest glimpse of the actor, on a fuzzy TV no less, but if you know what Theroux's voice sounds like, you might be able to recognise him.

And if that's not proof enough, rumours briefly did the rounds last year that Theroux had been cast in a mystery role, which quickly went quiet without any confirmation.

As it turns out, the leak was correct - also breaking that Dante Pereira-Olson had been cast in the film - even if Theroux's part only amounts to a mere 20-or-so seconds.