"Z Rock" is a unbelievably naughty show, but is it a funny show?

I've never heard of ZO2, and neither, probably, have you. They're an actual metal band struggling to achieve stardom, and I've never been much of a fan of the genre, so I'm obviously not enamored with their music. But they have this new show, "Z Rock," debuting Sunday on IFC, and it's a semi-improvised mockumentary in the "This is Spinal Tap" vein, so the more pressing issue is, are they funny?

(The gentlemen of ZO2 reflect on the finer aspects of crafting noisy music - oh, and banging as many groupies as time permits.)

The show's premise is that while they're waiting to become huge rock stars, they moonlight as a Wiggles-type kids act, playing upscale birthday parties and the like, only they're not so good at turning off the decadent rock-star thing when they're around kids. It's a funny premise; you just wish the execution were more consistent.

In Sunday's premiere, for example, there are two jokes about shaving pubic hair in the show's first five minutes. (Well, not jokes, really; just gratuitous references.) They land a gig to play a kid's show for a temperamental music producer who could make them stars, but the night before, get sidetracked with some groupies, so they arrive late to the assignment and discuss rather unsavory sexual acts in front of one of the kids and then it turns out that their recent conquests are really just horny soccer moms who turn up at the party and - well, you know; complications ensue.

The improvised dialogue often feels improvised in Sunday's premiere, which isn't a good thing, and the show features a lot of head-scratching celebrity cameos, such as Joan Rivers - hands, everybody: Any fans of raunchy heavy-metal comedy itching to see Joan Rivers?

But things pick up as the series progresses. Next week's episode finds the guys at a double-booked kids' party, performing alongside the jolly if passive-aggressive hacks of Kidtastic! and hating every minute of it. Conveniently, one of the band's former illicit conquests shows up at this party, too.

(Anyone want to bet that these T-shirts find themselves in a different configuration somewhere in the episode?)

An episode further in the future actually managed some solid laughs. The guys are shooting a music video, and former Jane's Addiction guitarist Dave Navarro has agreed to direct it. The whole celebrities-proving-they're-good-sports-by-mocking-their-personae thing has gotten kind of old, but Navarro is piercingly good at it, and he has so much to work with.

Navarro's vision for the video emphasizes their work with kids - the very thing ZO2 wants to get away from. But what he comes up with is in breathtakingly funny bad taste, an initially dopey vision that quickly devolves into scenes of children drinking shots of Jack Daniels and acting otherwise inappropriately in the way vixens usually do in music videos.

(By "Z Rock" standards, this is inordinately tame.)

Earlier episodes were rude for rudeness' sake; this one has some real bite. (What'd really be funny is if IFC put Navarro up for an Emmy in the guest-star-in-a-comedy category; watching members of those blue-ribbon panels pale as they watched this episode would be priceless.)

Not for kids or the faint of heart, "Z Rock" boasts robust nudity, vigorous simulation of sexual conduct and the sort of language that even I wouldn't use. On the strength of the three episodes made available for review, it starts out a little sluggish but definitely improves. ZO2 may or may not become heavy-metal heroes, but if their learning curve on "Z Rock" proceeds apace, they might make for a good comedy act.

They're still no "Flight of the Conchords," though.

- "Z Rock:" 11:30 p.m. Sunday; also 8:30 p.m. Tuesdays and 10:30 p.m. Fridays; Independent Film Channel.

(You know what this means, don't you? This show'll be debuting opposite the final half-hour of the closing ceremony of the most-watched Olympics ever. Good luck with that, guys.)