Amidst the feverish rumors of his imminent paternity, it’s nice to know that Ashton Kutcher can still make time to catch his friends acting like babies. Now in its fourth season on MTV (reports of the show’s cancellation being, surprise, a joke), Punk’d is offering less Kutcher, but otherwise, more of the same gotcha jokes on celebrities.

The 27-year-old Kutcher has gotten a lot of mileage out of his own modest, middle-American background (he grew up in Iowa and reportedly swept floors at the General Mills cereal plant before he started modeling). Punk’d plays off this populist yarn by turning its target-stars’ vanity into a giant “kick-me” sign.

This season, the Punk’d crew has already set its sights on Zach Braff, or, to be more precise, Zach Braff’s Porsche. When Braff and Scrubs costar Donald Faison stop at a liquor store to buy supplies for a poker game, Punk’d “field agent” Rob Pinkston (a very young looking 17) asks if they will to buy him beer. Brushing off the advance on his way into the store, Braff finds his cherished vehicle gaudily tagged. Straining to maintain his composure against his pint-sized antagonist, Braff lets fly with a string of expletives. The prank revealed and Braff’s bedside manner sheepishly restored, the actor submits to the self-effacement Punk’d routinely asks of its guests: “I can’t believe I almost beat up a five-year-old on national television,” Braff confesses. And yes, he looks silly.

Now that the series is well-known, Kutcher and company have upped some of their antes. They used an elaborate set — including an overturned mail truck and a burst fire hydrant — to convince The OC‘s Rachel Bilson that her dog was being held by the city until she pays for “damages.” When a representative from the water department shows up with a $35,000 bill for the run-off, good girl Bilson accepts the charge like it’s a parking ticket. Despite goading of the Punk’d cast (“The biggest problem we have today is you”), responding with sympathetically teary protestations.

As this episode shows, the subversive potential of Punk’d depends on a careful balance of hilarity and harassment, deflating the bubble of celebrity without it actually bursting. Victims who are good sports can be helpful, but those who are too nice, like Bilson, the trick can start to look mean-spirited. Consider the recent instance when Pinkston, playing a 10-year-old boy, begins to bother Dallas Mavericks forward Dirk Nowitzki for autographs. As Nowitzki and his friends try to eat their restaurant dinner, the boy returns to the table repeatedly, asking him to sign his napkin, and soon after, a bag full of sports paraphernalia (not all of it having to do with basketball) .It’s funny because the athlete is tripped up by this unexpected abuse of his fame and good nature. “The toughest thing in the world is saying no to a kid,” Kutcher mocks in the scene’s opening. Indeed, Nowitizki is reduced to signing a LeBron James jersey while muttering, “You’ve got to be kidding.”

Kutcher has said that one of his principal goals with Punk’d is to give young comedic actors a forum to hone their craft. (Dax Shepard, one of the early field agents, has since graduated to roles in Without a Paddle and the upcoming Mike Judge film, 3001.) If such paternal instincts seem at odds with Kutcher’s ’70s Show youthfulness, he does appear willing to exploit that very tension it for comedic effect. Introducing Bilson’s prank, Kutcher shares an anecdote about his much-speculated domesticity with Demi, recounting that he was awakened one evening to discover Moore’s dog was vomiting on him. This suggests not only his affection for dogs, connecting him with victim-to-be Bilson, but makes his humiliation exponentially worse than hers.

Kutcher is sophisticated enough to realize that social expectations, of parents, husbands, and movie stars, can never be wholly met. And in occasional and inevitable lapses, he finds humor. At its best, Punk’d lets the air out of celebrity long enough for us to recognize its impossibility and attendant responsibility. It’s humiliation tv for those who have too much. If targets’ reactions can be trusted, getting punked can be good for you.