Adam Pascal and Kerry Butler in “Disaster!” (Jeremy Daniel Photography)

NEW YORK — The year is 1979, and a porn-stachioed sleaze named Tony (Roger Bart) is packing his rat trap of a floating casino with enough comedy material to fill a Zucker brothers movie or two. Joining Tony on board for the casino's grand opening is the kind of gallery of characters that might have just missed going down with the SS Poseidon: a comely newspaper reporter (Kerry Butler) and the handsome waiter (Adam Pascal) she left at the altar; an outer-borough couple (Faith Prince and Kevin Chamberlin), one of whom is stricken with a mysterious pelvic-thrusting illness; and a lounge entertainer (Rachel York) singing for the supper of her twins, Ben and Lisa (both played by Baylee Littrell). And let's not forget the requisite singing nun (Jennifer Simard) and … some other people (Seth Rudetsky, Max Crumm, Lacretta Nicole).

Add a disco ball, a piranha-stocked aquarium and music from the heyday of Orleans and Melissa Manchester, and you've got a recipe for some serious '70s ridiculousness. Or as it's called by its creators, Rudetsky and Jack Plotnick: "Disaster!", the inoffensive, agreeably daffy musical spoof that had its official opening Tuesday night at the Nederlander Theatre.

As directed by Plotnick, "Disaster!" is intentionally cut from some pretty tacky cloth — a lot of it polyester, no doubt. So don't plunk down your hard-earned bucks thinking you're paying for "The King and I." Or even "Mamma Mia!" for that matter. This slapstick diversion puts into the throats of its vocally accomplished cast of Broadway vets the sort of music that's the subject of nostalgic TV pitches after 1 a.m. "Still the One," "Torn Between Two Lovers," "Hot Stuff," "When Will I Be Loved?" — the interpolated hits just keep on coming. It's a loopy brand of entertainment that is more likely to turn up in some cozy off-Broadway space, which is where "Disaster!" originated. It will be interesting to see if a parody of this super-relaxed variety can draw a Broadway crowd.

It is the caliber of these parodists that keeps the silliness afloat as Tony's earthquake-racked gambling vessel takes on ever more water. Butler, a star of Broadway's tongue-in-cheek "Hairspray" and "Xanadu," and Pascal, the original Roger in "Rent," approach their stock roles with a winning élan. As dyed-in-the-mink Noo Yawker Shirley (modeled on Shelley Winters's performance in the peerless 1972 upside-down cruise ship flick "The Poseidon Adventure") Prince gets to show off a gift for physical comedy that becomes more formidable with the worsening of Shirley's terminal illness — a condition apparently native to the Borscht Belt.

And Bart, the Carmen Ghia of Broadway's "The Producers," provides the vital services here of a polished clown. Best of all, though, is Simard's Sister Mary, a guitar-toting scold who cries "shame" at her shipmates' vices while harboring a secret yearning to shout "Blackjack!"

Disaster! by Seth Rudetsky and Jack Plotnick. Directed by Plotnick. Sets, Tobin Ost; costumes, William Ivey Long; lighting, Jeff Croiter; sound, Mark Menard; wigs, Paul Huntley. About 2 hours 10 minutes. Tickets, $65-$199. At Nederlander Theatre, 208 W. 41st St., New York. Visit ticketmaster.com or call 877-250-2929.