"LA CAGE AUX FOLLES" is a state-of- the-art Designer Musical, expertly eye- and ear-catching on its fine-feathered, sequin-encrusted surface.

But its rococo beauty is only skin-deep. Beneath the dazzling drag and blinding bugle-beaded sparkle, beneath Jerry Herman's dependably hummable melodies and Harvey Fierstein's witchy wisecracks, are an awful lot of padding and an empty hanger.

Playing at the National Theater, "La Cage aux Folles" spins dizzily around the endearing and enduring homosexual partnership of Georges, owner of a St. Tropez nightspot, and aging Albin, who endures the drab day to become dazzling diva "Zaza" at the club each night. Georges' son Jean-Michel, product of a one-nighter with a showgirl, is engaged to Anne Dindon, daughter of the ultraconservative leader of the Tradition, Family& Morality Party. So in preparation for a visit by the Dindons, Jean-Michel insists on hiding his father's lifestyle -- including Albin. So far, so funny, but the play falls apart disastrously with the arrival of Anne's parents.

Herman, Fierstein and director Arthur Laurents denatured this mildly risque material, making it so cuddly and wholesome you won't raise more than one eyebrow.

The book is peppered with "Torch Song Trilogy" author Fierstein's distinctively dishy one-liners, but for the most part Fierstein plays it sitcom safe and stale in order to be nonthreatening.

With familiar echoes of "Mame" and "Mack and Mabel" throughout, Herman's jaunty/schmaltzy score should shush the they-don't-make-them-like-that-anymore crowd. There are several gems here, most notably "Song on the Sand" and "I Am What I Am," but there is also generic filler like "The Best of Times," a calculated audience- rouser that could easily be inserted intalmost any musical.

As Georges, Peter Marshall is attractive and sings pleasantly, but he brings little emotional texture to the role, and several of Herman's best songs miss their tear-tugging target as a result.

As Albin, diminutive Keene Curtis fleshes out the character with a affectingly apt flamboyance. Looking like an unholy hybrid of Hermione Gingold and Truman Capote, Curtis finds his way to the dignity, defiance and hurt at the heart of "I Am What I Am"; lampoons the images of conventional manhood in "Masculinity"; and in the show's most successful number, "A Little More Mascara," executes Albin's miraculous makeover onstage while explaining the power of cosmetic thinking.

The other characters are cursorily sketched, and they are acted accordingly. Curtis' only real competition onstage comes from Ronald Dennis, a shameless scene- stealer as the outlandish butler Jacob. The wondrously leggy Cagelles -- perhaps better here than on Broadway -- create a remarkable illusion. Trying to discern the two real girls among the chorus line of nine is a challenge.

There are plenty of visual pleasures -- chief among them Jules Fisher's color-saturated lighting and Theoni V. Aldredge's extravagantly detailed costumes (three costume changes in the first number alone). And though they are alarmingly shaky at times, David Mitchell's shifting, sliding, snap-together sets create a series of fluid, cinema- style illusions.

Scott Salmon's choreography is fast- moving if unremarkable, relying overmuch on the always-popular kickline. The National's annoyingly tinny amplification seems unnecessary, robbing the brassy orchestrations and voices of their live theatrical presence.

LA CAGE AUX FOLLES -- At the National Theater through January 12.