NEW YORK -- Theatrical accident and my not having reviewed on Broadway since the Tony Awards created an odd serendipity: On the same trip, back to back, I saw two of the silliest possible musicals, "Xanadu" and "Young Frankenstein," and to my surprise I had more fun at the former.

Mel Brooks' monster comedy, which just opened Nov. 8, occasioned great anticipation: "The Producers" had showed Brooks could mine theatrical gold out of his film comedies. In contrast, who wanted to see a stage version of what I'm told was a sappy 1980 movie that no one much liked in the first place?

There's no doubt "Young Frankenstein" has the greater weight of craftsmanship and the greater length (about 2 1/2 hours), and you certainly see a lot of your money on stage. It lands all the expected jokes. But what about surprises? How can it measure up to Gene Wilder, Madeline Kahn and company? (I guess Nathan Lane and Matthew Broderick had a lot more to do with the success of "The Producers" than I realized.)

Weight is a two-edged sword. For all its silliness, "Young Frankenstein" seems awfully pleased with itself in a manner approaching pomposity, which ought to be the very antithesis of Brooksian irreverence.

When it opened July 10, "Xanadu" certainly had the advantage of low expectations. It was perfectly positioned to surprise people with its offhand, daffy charms. It is so slight that, at a bit over 90 minutes, it might even be a shade long. But it never claims to be more than the goofball it is, and it makes good on its claims.

'Young Frankenstein'

Not that there isn't fun in "Young Frankenstein," starting with whatever you enjoyed about the 1974 movie, with the exception of the cast and the fact that the jokes were newish then.

"What knockers!," "Where wolf?," "Not the lips," "Walk this way" -- the famous puns and strokes of caricatures are all in place. Lyricist, librettist Brooks, co-librettist Thomas Meehan and director Susan Stroman are all protective of the parody and jokes that are the reason the movie so lodged itself in the popular consciousness.

But the cast of two dozen is working awfully hard. Those dogged Transylvanian villagers have something dourly Teutonic about them, as though comedy were a matter of punching a time clock. I don't see the humor of the Hermit number. Silliness should have a lighter touch.

It does strike me that Brooks isn't quite getting a fair deal. We know the movie so well, we take its inspired lunacies for granted. If this were original, the perversion of the Frankenstein story would get more credit. But the same might have happened with "The Producers," except there Brooks provided more wit.

In "Young Frankenstein," too much of the humor is of the basic "mine is bigger than yours" variety, extending past anatomy to the sets themselves. But in both cases, bigger just isn't always better. Even Brooks' music doesn't add the brightness that it might, proving mainly utilitarian in spite of its parodic credentials: For example, I really like the mock-Weill sound of "He Vas My Boyfriend."

There are many pleasures in the cast. As the title character, Roger Bart is nicely understated, like a boy playing Errol Flynn, which sets up his manic eruptions. Sutton Foster is a funny, limber, Teutonic Barbi in the Teri Garr role.

Andrea Martin does as much as anyone could with the Mrs. Danvers parody, Frau Blucher, and if Christopher Fitzgerald doesn't quite measure up to the brilliant Marty Feldman, he's close. As the monster, Shuler Hensley is even better than Peter Boyle, intimating delicacy and heart behind his gross jokes. Only Megan Mullally falls far short, never approaching Kahn's comedy.

I loved "The Producers," so maybe my disappointment is compensation. "Young Frankenstein" is such that I'm not sure I'm looking forward to the musicalization of "Blazing Saddles" promised in the curtain call.

At the Hilton Theatre, 42nd Street and 7th Avenue; 1-800-755-4000.

'Xanadu'

The strike has doubtless helped "Xanadu," not just in bringing in more viewers but in creating the stress and frustration that makes such escapist fare doubly appealing. It's the perfect antidote to seriousness and even to top-heavy, insistent comedy such as Brooks'.

The book by Douglas Carter Beane, a deftly comic playwright, is all tongue-in-cheek. Seven of the nine Muses of Greek mythology find themselves transported to contemporary Venice -- California, that is. Their leader, Clio, disguises herself as the surfer chick/valley girl she already is in order to inspire (the muse's job) a handsome street artist, Sonny.

Their vision is that classic fusion of all the arts, a roller disco! But two of her sister Muses, Melpomene and Calliope, interfere. And there's a mogul whom Clio inspired in a previous generation who has to be reclaimed from materialism.

Maybe that all sounds somewhat pretentious, but it wears its sheen of education lightly, and Beane's book interweaves lots of wicked little digs. He's even added a reference to the stagehands' strike. The climax is all about the mythic power of leg warmers and excessive glitter balls. And the songs by Jeff Lynne and John Farrar provide a neon-flavored disco exuberance that pushes matters along.

Mainly, though, I love the daffy, accidental cuteness of Kerry Butler as Clio, who convinces me the Greeks would have given Clio roller skates if they'd known about them. She is nearly matched by the cluelessness of Cheyenne Jackson's dumb but pretty Sonny, and Mary Testa and Jackie Hoffman add light comic villainy.

Tony Roberts plays the mogul but he was on vacation, and his understudy, Peter Samuels, filled in well. Even the intimate Helen Hayes adds to the fun.

At Helen Hayes Theatre, 240 W. 44th St.; 1-800-432-7250.