”This is like children’s theater for 40-year-old gay people.” So says one of the characters in Xanadu, thereby rendering any further criticism unnecessary. Whether you find Broadway’s newest offering to be (a) fun summertime fluff or (b) the end of musical theater as we know it will depend on your feelings about the source material, the stupefying 1980 Olivia Newton-John vehicle/camp touchstone.

The barely intelligible story features Clio (Kerry Butler), one of the muses, descending from Mount Olympus to Venice Beach on a mission to inspire Sonny (Cheyenne Jackson), a suicidal pavement artist, to open a roller disco. (The logic: A roller disco combines all the arts in one beautiful entity.) Given the mandate to spoof this supremely silly material, librettist Douglas Carter Beane abandons the prickly Hollywood satire he showed in last season’s Tony-nominated play The Little Dog Laughed, coasting instead on easy jokes about Andrew Lloyd Webber, Les Misérables, and Clash of the Titans. The songs — save a couple of guilty pleasures like ”Magic” and ”Evil Woman” — consist of enough disco-lite B-sides for one those ’70s tributes that run on PBS during pledge week. And they’re not helped by Dan Knechtges’ choreography, which (aside from impressive stunt roller skating) mostly tries to wring laughs from stilted dance-floor moves.

Butler deadpans her way through the role of Clio, amusingly sending up Newton-John’s Aussie accent and vocal mannerisms. Clad in denim shorts, tube socks, and a headband (!), Jackson — an 11th-hour sub for injured lead James Carpinello — gives Sonny a goofy charm and sex appeal. Tony Roberts, always a pro, does double duty as Clio’s aged ex and a grumpy Zeus. (Clio serenades him with a rendition of ”Have You Never Been Mellow?” which would certainly make me grumpy.) Mary Testa and Jackie Hoffman ham it up ferociously as Clio’s rival muses — at one point, Hoffman literally tries to eat the scenery — although, admittedly, the sight of the Junoesque Testa in a Medusa wig is pretty tasty.

Surprisingly, this grossly overextended comedy sketch got a free pass from the critics, who were apparently relieved that it wasn’t a total train wreck. There’s an audience for Xanadu — you know who you are, and you’re certainly welcome to it. But this better not be the start of a trend. Note to any producer eyeballing the stage rights to Can’t Stop the Music: We will hunt you down. (Tickets: or 212-239-6200) C