In the way that teenagers are proud of their explicit lyrics, playwrightdirector John Clancy is proud of the acidic humor in “Fatboy,” which opened yesterday at the Ohio Theatre. “Fatboy” is crude, inundated with profanities, and ruthlessly caustic. Based on Alfred Jarry’s 1896 absurdist farce, “Ubu roi,” Mr. Clancy’s play is a live-action Punch and Judy show about a monstrous fat American who likes to murder people. Alas, what was shocking a century ago feels tired and self-congratulatory today. In the end, these 80 minutes of concentrated bile amount to a smart but adolescent stunt.

To see the hackneyed masquerading as the shocking is nothing new in downtown theater, but “Fatboy” is a prototypical case. After the usual procession of blacker-than-black jokes (about eating babies), oversize pointy bosoms, creaky song-and-dance comic relief, and breaking-the-fourth-wall bits about costume changes, one wonders: What next? A boy in a dog collar? And sure enough, out comes the requisite boy in the dog collar.

Perhaps this is all part of Mr. Clancy’s design; Perhaps, one thinks, his intent is to deploy the usual grotesque elements to original ends. Certainly he is adept at getting under one’s skin. It’s disturbing to watch Fatboy (Del Pentecost) chew up a wooden chair. It makes one squeamish to watch his grossly sexual wife, Fudgie (Nancy Walsh), strip a lover down to his sock-stuffed briefs. Most effective of all is the play’s oft-repeated device of giving one actor a rousing noble speech (“Prejudice holds no weight here!”), then having the characters collapse into raucous, indecent laughter. )To them, morality is one big, ludicrous joke.)

The problem is that after taking pains to make his audience squirm, Mr. Clancy has nothing particularly original to say. His message is by now quite familiar to both liberals and conservatives: Fatboy (read: America) is out of control, gobbling up bodies and nations, riding roughshod over human rights, governing according to the whimsical appetites of a monster. The implied conclusion is that compassionate, moral people who “get it” should stand up to the monster.

There is nothing nuanced in this message – though, to be fair, the Punch and Judy absurdist theater is not the place to go for subtlety. “Fatboy” is obviously exaggerated. After all, if its sweeping assertions were true – if human rights violations no longer mattered, if villages could be razed on a whim, if individuals had no power against the state – they would hardly be laughing matters.

Yet the play takes its own exaggerations too seriously, and that makes it feel adolescent. In the final scene, when Fatboy removes his fat suit and looks the audience in the eye and speaks quietly, he says, with undisguised sarcasm, “You know that none of this is real! Monsters don’t exist!” What he means, of course, is that you’re a dupe if you don’t see how accurate the caricature is.

The fact is that the play’s over-thetop obscenities, sexual content, and black humor are now staples of mainstream entertainment. Far more innovative and interesting are its puppet show-like proscenium stage, its actors’ high-pitched, vaudevillian delivery, and its playful fracas with Shakespearean language in the third act.

“Fatboy” evidently thinks itself quite radical politically, yet it does little but preach to the converted. When “Ubu roi” had its notorious premiere, audience members stood up and yelled and shook their fists; Jarry had to move his play to a marionette theater. On Sunday night, the “Fatboy” audience hooted and chuckled, and during Fatboy’s final earnest plea for change, the crowd received his message warmly. For all its vicious, button-pushing material, “Fatboy” seemed to go down like pablum for its self-selecting audience. Like a radio shock jock, “Fatboy” gives its demographic exactly what it expects.

Until March 25 (66 Wooster Street, between Spring and Broome Streets, 212-868-4444).