We're talking heavy. How heavy? Take the nine minute Pink-Floyd-on-steroids opus "Eclectic Electric," which enlists two of the more hirsute guitar players you'll hear in this lifetime (who also happen to be good friends of the band), Metallica's James Hetfield and Jim Martin, formerly with Faith No More. Of course, what would a little friendly collaboration be without the obligatory legal bullshit? "Pseudo-Mexican" Primus drummer Brain raises his eyebrow.

"Yeah, we got the big letter after we did that," he says. "It said something like, 'If you mention that James Hetfield or Kirk Hammet has played on this, you know, your balls will be cut off.' Metallica is an institution, they're probably Elektra's biggest band. It's just like, you can't use any of their names, it's just the way it is. So they came as friends, and you know and I know, but I guess we can't put it on the album. You can write about it, we can say it, we just can't credit them."

The San Jose, California native then gets reverent. "So here's Jim Martin, Kirk Hammet, and James Hetfield, just the metal guitar guys. And we made this really out tune that we were jamming on and they came in and were laughing at it, 'What the fuck is this? Is this some disco song or something? Come on!' But we just turned on the tape and let them both go, James and Jim in the room. It was insane, you just hear James Hetfield and go, fuck yeah, that's the way you play that stuff! Everything was just chunk, chunk, chunk."

AntiPop is chock full of bizarre incestuous combinations, including Limp Bizkit vocalist Fred Durst, who produced Primus's most skate-punk friendly song to date, "Laquerhead."

"Fred's kind of the Puff Daddy of rock kind of vibe," Brain says. "He's cool, wants to be involved in everything, do everything. There's just this vibe with him, he comes in and he'll stand right next to you and make you play harder. It kind of reminds me of how when the Chili Peppers said they got George Clinton to produce. I can see how it would be kind of the same, because it's more about just going in there and yelling and trying to get your energy going."

Juxtapose to that the production help on the almost Zenyatta Mondatta-ish "Dirty Drowning Man" from former Police drummer/now classical composer Stewart Copeland. Drummer Brain remembers the first meeting with his idol.

"He called us and told us to come down to his place in LA and just jam," he says. "We go into SIR studios, and there they are, the Police drum set with old, beat up heads on 'em. My drums are set up right next to his, and I start playing. He runs in the room and starts playing and I was like oh shit! But we had a great time and he said, 'Let's do something,' and he ended up coming to Les's house, Rancho Relaxo."

"Even though we didn't really have anything that much in common in the sense of what he's doing now musically, and we're generations apart or whatever, he was into everything I was into, but in a different way. I was like, 'Yeah man, I'm totally into golf because it's about dressing up and eating good food and spending money.' And he was like, 'Oh yeah? Well you've got to check out

Matt was really into that Led Zeppelin tune 'Fool In The Rain,'" he explains. "And I used to be in a band called Ted Zeppelin, doing Led Zeppelin and Ted Nugent covers, so you know, I studied that stuff. But we never did that song. So Matt and I went to the record store and bought the disc and I learned that shuffle groove for him and it just kind of developed into the groove on 'Natural Joe.'"

Of course it must be mentioned here, in case you aren't aware of the titanically successful animated TV show, Primus also performs South Park's theme song. Brain remembers, "That was the first thing I ever recorded with Primus, about three and a half years ago. They sent me this tape of the cartoon, and I was laughing--it was insane. We did it for free, just as a favor, and the thing blew up." Did we mention the cartoon was titanically successful? "Trey and Matt didn't really know it was going to do that either. They sold their T-shirt rights for like $3,000."

If you're thinking the AntiPop sessions were somewhat of a bitch to coordinate because of all the collaborations, you would be right. It took a little over a year "off and on," to be not quite exact.

"Because what we did at the beginning, the record company wanted us to get a producer, one of the producers that's doing all the hit records now," he explains. "And we thought that was cool, but we thought we'll just sound like those albums. It'll just be Primus with the same sound as Korn or Limp Bizkit or Rage Against The Machine or whoever. We thought, why don't we just make a wish list of not so-called producers but just friends or artists that we respect? So we just made a list and almost every one of them was interested."

The collaboration with Tom Waits was actually more of a reunion, as Waits lent vocals to the Seas Of Cheese favorite, "Tommy The Cat." "He was rad," Brain exclaims, "He came in to do Coattails Of A Dead Man,' and said, 'We can produce this song. I don't want no money. I'm just coming as a friend to help you out.' It was rad. And then we played on his stuff [Tom's Mule Variations]. Of course, we got paid. I need the money, Tom doesn't."

A lot of Primus's makeup, personally and musically, is fraught with humor. There's the well-regurgitated story that Les Claypool auditioned for Metallica and failed after suggesting they jam out to an Isley Brothers tune. When Primus opened for Rush at a Bay Area show a few years ago, a reverent Les promised, "You're going to jizz all over yourselves [when Rush comes out]." Even Brain's joining the group has tongue-in-cheekiness to it.

"I joined about three and a half years ago," he explains. "I was in Los Angeles doing sessions, trying to work on movies. I had just done the drums for Mortal Kombat, and was doing a little touring with Bill Laswell and Buckethead, Praxis. And Les called me one day, and it was funny, he was like, 'Hey Brain, what if the Red Hot Chili Peppers called you and asked you to join the band?' I said, 'I don't know, I'd check it out I guess.' Then he said, 'Well, what if Ozzy Osbourne called you and said, hey we need you as a drummer?' I said, 'I don't know, whatever.' Then a week later he calls and goes, 'Hey, how do you feel about maybe playing with Primus?' And I just figured I would check it out. At the time, I didn't want to do the rock thing, the band thing. Because I had more fun producing break records and doing session work with Bill and doing loops and playing on everybody else's albums. More of a session guy in LA. But it's actually helped me out a lot, it was probably the best move I could have made. It's done for me what it did for Herb. [Former Primus drummer Tim "Herb" Alexander] Primus is a drummer's band, in the sense that they allow the drums to get off."