On a balmy autumn afternoon, business at the Chateau Marmont’s restaurant is brisk; no one works 9-to-5 in L.A., evidenced by the bartenders already straining ice-flecked vodka into martini glasses. Silver-haired sugar daddies eye sculpted women materializing in clouds of $220 perfume, and waiters practically bow to everybody. There are probably several famous people seated in the dining room, but c’mon, act like you’ve been here before. This is Hollywood’s cafeteria, and you can’t sit with them, anyway.

Kicking back in his chair and rolling his eyes, Charlie Day plays his part, the archetypal class clown observing from a distance. “This place,” he mutters, amusement and disgust threaded in his voice as he surveys this scene of scenes. The irritation is probably compounded by Day being more into daddy duty with his five-year-old than sugar daddy duty. Scratching the side of his mussed hair, he jokes about Kim Kardashian complaining about a dessert fork’s misplacement, and the disgraced waiter’s body subsequently being hauled to the desert.

Despite evidence to the contrary—a respectable resume that includes both a long-running black comedy that helped usher in the golden era of television (It’s Always Sunny in Philadelphia) and a big sci-fi blockbuster (Pacific Rim), a wife who’s also in the business, a house in the (Los Feliz) hills, this Marmont waiter deferring to him—Day has always seemed a bit of an outsider in Hollywood. Turns out, there’s some truth to that. The script for his new movie out on February 17th, Fist Fight, which co-stars Ice Cube and Day as teachers who duke it out after school, was being batted around New Line Cinema. Day searched it out, not the other way around.

“If I didn’t hustle to get movies made or write original things and sell them, I don’t think you’d see much of me,” Day, 41, says, popping an olive in his mouth. “The phone wouldn’t ring that much. Or it would and I’d feel like I had to take what was offered. I’ve been able to avoid the low-hanging fruit.”

In 2005, Day and two other struggling actors, Glenn Howerton and Rob McElhenney, spent $200 to shoot a pilot that would become It’s Always Sunny in Philadelphia, a sitcom about a group of pals who run an Irish bar in Philadelphia. FX marketed Always Sunny as “Seinfeld on crack.” “The Gang,” as they’re dubbed, is sort of like the crew on Friends if Ross, Rachel, Monica, Chandler and Phoebe huffed paint and hatched plans to game the welfare system. Twisted, brilliant, and teeming with controversy, the show is still on the air after a decade, and at least two more seasons are on the way. It’s a hell of a show, and as an executive producer, writer and star, Day is at its center for good reason. Racing just below the top layer of his performance is a frenetic energy that imbues his every move with electricity. He’s a magnetic presence on screen, yes, but your eye also gravitates toward him because he seems right on the brink of falling off a cliff. He never does, but that internal balancing act means he’s always in motion—thus naturally always drawing the audience’s attention. It’s a shrewd play.

“People see him as this crazy character he does so brilliantly, but they don’t know he’s probably the smartest actor I know,” says Richie Keen, the director of Fist Fight and a couple seasons of Sunny. “In drama, there are always at least a handful of ways to do something in an interesting way. In comedy, it’s pretty binary. People laugh or they don’t. Charlie’s hit ratio—what his instincts are and what makes people laugh—is almost a perfect score.”

Yet Day is right. Sunny hasn’t set his career on fire the way similarly iconic shows have for some of his contemporaries. Even though comedy is harder to play than drama, comedic actors generally have a harder time transitioning to movie stars, and when one does, it’s generally with a dramatic role (think Adam Sandler and Punch-Drunk Love or Jim Carrey and Man on the Moon).

Then again, he really doesn’t care about any of this.

“Truly, I’ve always been so happy to have the opportunity to do this that I’ve never felt like, ‘Oh, I want to be doing that.’ Maybe someday I’ll do drama—and if people don’t like that, they can go fuck themselves,” he says, laughing.