Longtime fans of the Beastie Boys could be forgiven for imagining that the rappers would be perennially young, forever New York’s impish hometown heroes, ollieing past authority on their way to after-hours fun.

In truth, Adam Horovitz, 48 and better known as Ad-Rock, hasn’t set foot on a skateboard in a decade. “It’s way too much work,” he said. He doesn’t rage the way he did in the old days, either. “I’m certainly not going to take ecstasy and hit the club and listen to whatever, like, electronic dance music hit,” he said. “I got no business going to a club. I’m a terrible dancer. I got a bad back.”

All of this made him, in some ways, perfect for the part of an early-to-bed, stay-at-home, sweater-wearing New York dad in Noah Baumbach’s new movie, “While We’re Young.” The art-filled apartment, the casually mussed gray hair, the Wilco collection — “I’m pretty much that person,” Mr. Horovitz said. “Except for the Wilco CD.”

The comedy, which opens March 27, stars Ben Stiller as a stalled midcareer documentary filmmaker, with Naomi Watts as his film producer wife. Their personal and professional lives are turned upside down when they meet a young Brooklyn couple, played by Adam Driver and Amanda Seyfried, who bicycle everywhere, make artisanal avocado ice cream, and prefer VHS tapes and typewriters to digital files.