Ben Stiller has been near the center of American culture for nearly 40 years, from “The Ben Stiller Show” in the early ’90s to “Reality Bites” to “Zoolander” to “Meet the Parents” to “Tropic Thunder” to his work behind the scenes of the Apple TV+ smash “Severance.” But that’s all showbiz stuff; none of us have ever really known the man himself. To see the real Ben Stiller, the human being beneath it all, you have to watch a Knicks game.

Stiller, over the New York Knicks’ run during this NBA playoffs (and really throughout this whole season, their best in more than two decades), has established himself as the unofficial fan in chief of the team. And he has done it in the best possible way: by being a truly insane Knicks fan. During games, Stiller leaps, he screams, he frets, he mopes, he loses his ever-loving mind — he even, somehow, tweets obsessively, something he has been doing all season, long before the bright lights of the postseason. You don’t really know your legendary comedy stars until you have watched them angrily pound complaints into their phone after a Jalen Brunson non-foul call on a random night in February. (Or made a cameo in a niche Knicks music video on X.)

ESPN and TNT have spent much of these playoffs showing Celebrity Row at Knicks games; for the first time in a long time, there’s no cooler place to be seen than courtside at Madison Square Garden. But what’s different about this new group of Knicks fans — your Stillers, your Bad Bunnys, and yes, your Timothée Chalamets — is the sheer intensity of their devotion. They love the Knicks the way all die-hard sports fans love their teams: unabashedly, unreservedly and irrationally. And in this, they reveal their true selves. When are celebrities truly most like us? When they are sports fans.

One of my favorite interviews of the last decade came when Ben Affleck appeared on former sportswriter Bill Simmons’ long-canceled, long-forgotten HBO show “Any Given Wednesday with Bill Simmons” back in 2016. This Affleck was not the unknowable mega-celebrity of paparazzi, tabloid covers and “Argo.” He was a ranting, raving lunatic, talking about how there was a “conspiracy” against New England Patriots quarterback Tom Brady, how it was all guys who “work for the f–king Jets” and calling the was-there-enough-air-in-the-footballs controversy known as Deflategate “the ultimate bull—t f–king outrage.”

This led some observers to try to claim that Affleck was drunk or out of control, but any sports fan — particularly any Boston sports fan — recognized this Affleck instantly, because that passion, that desperate no, no, you don’t understand, they’re trying to screw my team, is precisely how all of us talk. All the celebrity, all the Oscars, all the famous girlfriends and wives, all the pap walks, it all vanished instantly: Affleck was just a fan.

You’ve seen the way fandom reveals a celebrity’s true nature constantly throughout these playoffs, and no offense to Superfan Stiller, but it is Chalamet who has become the unofficial Knicks mascot this postseason precisely because he so obviously cares about this team so much. Chalamet has a long history as a Knicks fan. He once, as a child, met long-forgotten Knicks Landry Fields and Andy Rautins in Grand Central Terminal, winning an online contest and scoring free tickets to a game. Amar’e Stoudemire actually remembers meeting him when Chalamet was 14. He has embraced this particular Knicks team with the fervor of a man who has waited his entire life for his team to be good.

Chalamet seems more ecstatic about this Knicks revival than he could ever be about some dumb Oscar. He skipped the Met Gala for a Knicks playoff game and has basically been treating the Knicks as a never-ending tour since. He has screamed at the refs for them to call a tech on the hated Indiana Pacers guard Tyrese Haliburton, posed for a photo with Spike Lee (and sat with Stiller), and celebrated so hard with Knicks fans after they beat the Boston Celtics that the teeming masses literally almost pulled him out of the back of a black car. (And he very much did not seem to mind.)

Chalamet is so dedicated to these Knicks that he has been sitting courtside (and still screaming) even on road trips; it really is quite something to see the wispy, elfin, thinly mustachioed Next Great Actor every night in Indianapolis.

There are other die-hard celebrity fans throughout the sports world; Paul Rudd loves his Kansas City Chiefs, as do Eric Stonestreet and Melissa Etheridge. Jon Hamm and Andy Cohen love their St. Louis Cardinals. I’m pretty sure Matthew McConaughey would renounce his entire acting career to play one down for his Texas Longhorns. But it is undeniable that part of the aura Madison Square Garden has had during this playoff run — with a huge Game Five at MSG slated for Thursday night — has been from the unusually pure engagement that Celebrity Row has with this team and its stars. At this point, if you saw Chalamet or Stiller get a technical foul, would you be the least bit surprised?

We spend so much time trying to figure out what makes our celebrities tick, what parts of them they show to the public and what parts they keep hidden. We want to know who they really are. But they are never more truly human, unguarded, electrified, alive, than they are when they are cheering for their team.

I often joke that the best thing about sports is that it’s one of the two things that will make me spontaneously jump in the air and start screaming. (The other is a spider.) Being a sports fan means losing control of your emotions, it means a shedding of all the masks we wear the rest of the day. We are never more truly ourselves than we are cheering for our favorite team. That’s true of you, that’s true of me, and that’s true of Chalamet and Stiller. I don’t know them. How could I? But when they’re watching the Knicks — my Knicks, our Knicks — I am them. We all are.