Bands in costumes usually bug me a lot, in large part because most of them don’t bother to explain exactly why they’re dressed the way they are. I mean, I dig KISS and everything, but usually about two-thirds of the way through their concerts, I start thinking “Okay, I get what they’re supposed to be . . . but what, precisely, are a space alien, a demon, a star and a cat doing up there on stage together?

And it gets even worse for me when it comes to the nü skül metal mask bands like Slipknot or Mushroomhead or Mudvayne. I think the stupidest, most pointless thing I’ve ever seen onstage at a rock concert, for instance, was the idiot in Slipknot with the sex toy for a nose crouching on a pile of drums that he wasn’t playing, shaking his nasal money-maker at the crowd, booga booga. Pointless and dumb. And pointless some more.

Which, I suppose, GWAR are too, but at least they’ve got a concept of sorts to explain why they’re dressed the way they are, and they’ve been nothing if not consistent in adhering to that concept over the years. See, the idea is that a marauding band of pirate aliens called the Scumdogs of the Universe were banished for their affronts to Earth, the most godforsaken ball of dung in the known universe. After killing the dinosaurs, creating humans, and sinking Atlantis, the Scumdogs were imprisoned underneath the Antarctic ice for millions of years — until being dug up by promoter Sleazy P. Martini and put on the road as GWAR, the rock & roll band to end all rock & roll bands.

Thing is, though, that GWAR’s members — singer Oderus Urungus, guitarists Flattus Maximus and Balsac Jaws of Death, bassist Beefcake the Mighty and drummer Jizmak da Gusha — like making rock music, but they like massacring their onstage enemies even more, usually resulting in copious quantities of bodily-fluid colored goo being projected into the audience. Their stop at Saratoga Winner last Friday found GWAR promoting “Blood Drive 2002,” doing their part to fill the coffers by hacking their way through a motley bunch of latex dummies, Mike Tyson, Osama bin Laden, President Bush and Pope John Paul among them.

Terrifically offensive, you bet, but you shoulda seen the 800 people packed in the room screaming and pushing and jumping, hoping to get some (simulated) viscera tossed their way. Pretty much exactly like the other GWAR shows that I’ve seen over the years, with a couple of exceptions that only the converted would have noticed: longtime GWAR woman Slymenstra Hyman was absent (she’s got her own freak-based road gig now, called Slymenstra’s Girlie Show), as were Sleazy P. Martini and the Sexecutioner. (Bummer, huh?) And I couldn’t tell, in the murk, whether it was Techno-Destructo or Bozo-Destructo who came out to pull off the top of Oderus’ skull at the end of the set. I’ll be a lot of others lost sleep over that, too.

But, troubling, unresolved questions aside, GWAR put on yet another great show, equal parts Nickelodeon Slime Time, Grand Guignol atrocity exhibition and World Wrestling Federation cage match. Oh . . . and the music? Well, uh, it was loud, and there were guitars and stuff and, um, it was loud. I’ll pay better attention to it next time, honest.