Penn has now been in high school for the better part of seven years, and he's over it. This is his fourth prime-time series. He was a high-school student in Do Over in 2002 and in The Mountain in 2004. He briefly advanced to college in The Bedford Diaries in 2006. Now he's been demoted back to high school (at least he's a senior; the Gossip cast will graduate this season, and not a minute too soon). He knows it's funny. "We all look way too old," he says. "But if we looked the right ages, some of the scandalous shit we do on the show would be too much." (Ironically, in real life Penn skipped high school altogether. He took a proficiency exam at 14 and entered Santa Monica College soon after.)

Penn, who's 21, is funny and articulate, if prone to the occasional conversational misfire that makes you want to hand him a rewind button. Example:

Penn on the paparazzi: Sometimes it's like, I wanna walk my dog, and I can't, because there might be photographers.

Me: You have a dog?

Penn: No. Everybody else does, though.

Penn's girlfriend, not incidentally, is Blake Lively, who plays the blonde reformed sinner Serena van der Woodsen (and who, it should be noted, does have a dog). Every public sighting of the couple is documented and snarked upon by webloid culture (PopSugar headline: ARE BLAKE AND PENN CUTE OR ANNOYING?). Penn, who was home-schooled with Blake a decade ago, when both were child actors, calls the relationship "wonderful and also something to grapple with" in terms of mixing work and pleasure. But he won't say more. "You have to draw the line somewhere. I'm fine talking about my family and personal history, because it humanizes you. But I have to save some shit for me."

Penn on screen with Blake Lively, his girlfriend on and off the show

Penn tells me that "one of the things that's been my bread and butter with all these television shows I've done is that I don't give a shit," that he initially turned down Gossip Girl, doesn't care for learning his lines, thinks his character is too judgmental, and dislikes most theater, TV, movies, contemporary rock ... Please! This is all sounding too world-wearily Brangelina-esque for a 21-year-old. And he knows it. "People who don't know me that well often think I'm a bit of an asshole and take myself too seriously," he says.

What are they missing? I ask him.

"That I don't take anything seriously. And that just because I'm not smiling doesn't mean I'm not happy. Chace is one of the most positive guys I've ever met, and you can see that in the way he walks around. I'm also like that but you can't see it."

For the record: Penn is not an asshole, just a guy who protects himself with a light veneer of cynicism. Which may be a smart way to cope with the noise around Gossip Girl. He's been here before, he's had people bullshitting him that it's all going to break his way, and this time he's building himself some insulation. He didn't grow up poor, but his parents divorced when he was 12, and there were lean-ish times after he and his mother, who'd worked at Home Depot, left Washington State for California so that he could pursue acting. For him, acting is work it's how you make sure you can pay for your own car and make your rent. And if you need to shave your chest hair because teenage girls find chest hair on a good guy sexually threatening, you get out the razor. It's a living.

I ask him about the difference between not taking things seriously and doing a half-assed job. "That's a line I make sure to walk carefully now, because I didn't always," he says. "When I'm bored, my voice becomes even more of a monotone than it usually is. I have to check myself sometimes." As the interview goes on, Penn brightens. He talks about his love for writing music and his excitement about shooting next year's horror remake of The Stepfather. "Suddenly I thought, I like taking chances!" he says. "I want to continue to take chances! Okay, now I understand what people are talking about!" Early in our conversation, I'd asked him what he'd like to change about himself in five years. He drew a blank. Now he spontaneously returns to it: "I hope in five years," he says, "I no longer look at acting as a job but as a creative passion. That's how I want to be different."