To say Beau Is Afraidis a wild ride is an understatement.

Ari Aster's latest film, which Mashable's Kristy Puchko describes as a "three-hour-long panic attack as cinema," depicts anxiety-riddled Beau's (Joaquin Phoenix) odyssey home to see his mother Mona (Patti LuPone). His journey includes a nightmarish cityscape, a hypnotic stage, a horrifying penis monster... and one extremely unexpected cameo.

When Beau calls his mother early in the film, a UPS delivery man picks up the phone. This stranger has found Mona's body, its head crushed to oblivion by a chandelier. The following scene, in which Beau and the UPS guy try to process what's going on over the phone, ends up being one of the film's most darkly funny sequences.

It's no surprise, then, that the UPS guy would be played by an actor who is no stranger himself to finding the humor in darkness: Bill Hader. The Saturday Night Live alum also co-created and stars in HBO's equally twisted Barry, now in its fourth and final season. (Hader directed every episode this season.)

Bill Hader's cameo in Beau Is Afraid is not just limited to his voice work. We also see him briefly in a news report about Mona's death, where he has his back to the camera and definitely does not want to be talking about finding a famous woman's corpse.

In an interview with Deadline, Hader described shooting the initial phone call scene with Phoenix. Hader delivered his lines over the phone to Phoenix throughout the one-take scene, trying vastly different approaches for each take. "My assistant was like, 'What the fuck are you doing?'" Hader told Deadline. "'You’re just crying and freaking out…' Because we did some takes that were really wild, really big and intense."

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He continued: "I just remember feeling really exhausted and Ari coming on and going, 'Hey, man. It’s so funny, Bill.' And I was like, 'Funny? I can’t see straight. I’ve been crying.' But they just thought it was hilarious."

Beau Is Afraid is now in theaters.