WHO wouldn't want to go back to the New York City of 1954, the year celebrated in the new musical "My Favorite Year"? As Benjy Stone (Evan Pappas), the show's young hero, reminds the audience, 1954 was the time of beefy Buicks and a hit parade dominated by Kitty Kallen. A time when Fifth Avenue was a two-way street and "everything had chlorophyll in it." Most of all, as far as "My Favorite Year" is concerned, it was the Golden Age of live television, as exemplified by "The King Kaiser Comedy Cavalcade," a weekly 90-minute NBC variety show that resembles Sid Caesar's "Your Show of Shows" and for which Benjy is the bright-eyed freshman gag writer.

"My Favorite Year," which opened last night at the Vivian Beaumont Theater, not only wants to re-create that halcyon time, from its Breck girls to its Formica decor, but it also wants to do so in the wonderfully retro Broadway musical-comedy style of the same period. Nineteen-fifty-four was also the year of "The Pajama Game," whose Bob Fosse choreography this show passingly mocks. From its opening number, a sort of "Comedy Tonight" set in a television studio, "My Favorite Year" offers the happy promise of a new musical in the hilarious manner of "Pajama Game" successors like "Bye Bye Birdie" and "Little Me" written by "Show of Shows" alumni.

So why does "My Favorite Year" fail to sustain that lighthearted spirit, or even to replicate the modest farcical charms of the nostalgic 1982 Hollywood movie that is its source? These are questions that can be answered only by its gifted creators: the writer Joseph Dougherty (of Off Broadway's "Digby" and television's "Thirtysomething"), the songwriters Stephen Flaherty and Lynn Ahrens (of "Once on This Island") and the director Ron Lagomarsino (of "Driving Miss Daisy"). Whatever the cause, "My Favorite Year" proves a missed opportunity, a bustling but too frequently flat musical that suffers from another vogue of the 1950's, an identity crisis.

The evening's assets, which include a superior supporting cast led by Andrea Martin and Lainie Kazan, a few good jokes and a zippy physical production, are outweighed by such major failings as the questionable casting of the starring roles and a disappointing score. But this musical's overriding problem, from which all the others spring, is its wayward tone.

For a few scenes, "My Favorite Year" follows its screen progenitor, telling the dizzy backstage yarn of how the green Benjy must baby-sit his television show's guest star, a drunken and reckless Errol Flynn-like movie legend named Allan Swann (Tim Curry), during a frantic week of marathon rehearsals. But by the end of Act I, the musical has radically altered its focus and mood (and dismantled its plot) to concentrate on Swann's tortured relationship with his neglected, nearly adult daughter (Katie Finneran) and on Benjy's courtship of a humorless production assistant (Lannyl Stephens) far drippier than the equivalent heroine of the film.

Certainly Mr. Dougherty and company have no obligation to be faithful to their source, but they never give the audience a reason to care about the new direction they take. The two women who captivate the male leads for most of Act II are bland, underwritten nonentities whose interchangeability extends to their Barbie-blond hair. Concurrently, the relationship between Swann and Benjy turns dour, to the extent that it is dramatized at all. Swann's comical drunkenness all but evaporates, and Benjy becomes psychologically fixated on replacing the father who abandoned him in childhood.

As Sid Caesar, King Kaiser or Molly Goldberg might say, oy!

It is impossible to tell whether the casting of "My Favorite Year" or its libretto is responsible for the transformation of Swann and Benjy from clowns to sentimental straight men. While Mr. Curry and Mr. Pappas are both first-rate musical performers, each seems out of sync here, at least as directed with a heavy hand by Mr. Lagomarsino.

In the Peter O'Toole role, the fit and young Mr. Curry seems neither dissipated by drink nor remotely old enough to have starred in the 58 swashbuckling movies Swann is said to have made. His huge comic talents are hardly called upon after his initial entrance, and he eventually is capsized by repetitive back-to-back songs (before and after intermission) that require him to engage in melancholy introspection. The hyper energetic Mr. Pappas, whose intense antihero dominated last year's Off Broadway revival of "I Can Get It for You Wholesale," plays Benjy (Mark Linn-Baker on screen) as a moody literary cub, more of a cloying, aspiring novelist than a Hollywood or Broadway-bound purveyor of punch lines.

You know a musical is in trouble when the minor characters consistently upstage the leads. It's no secret that Ms. Martin, of SCTV reknown, is a terrific comedian, but in "My Favorite Year," she brings to the role of a wisecracking comedy writer not just dry timing and nutty voices, but also razor-sharp skills as a burlesque dancer, pratfall artist and satirical chanteuse in the Imogene Coca tradition. It's one of the authors' more conspicuous lapses that the big number they give to the deserving Ms. Martin, "Professional Showbizness Comedy," fails to live up to its title.

As for Ms. Kazan, who repeats and expands upon her film role as Benjy's meddling Jewish mother, her uncompromising excess is hard to resist. She steams through "My Favorite Year" like a top-heavy ocean liner that has lost its compass, and she has been costumed accordingly by Patricia Zipprodt, the wittiest artist in the production's design team. Ms. Kazan also retains a belter's singing voice and, fittingly, has been handed the only two melodies in Mr. Flaherty's score with immediate staying power. But one of them, "Rookie in the Ring," is a digression that brings the show to a deadening halt, and the other, "Welcome to Brooklyn," is robbed of its potential theatrical bravura by the woefully stock musical staging of Thommie Walsh.

Tom Mardirosian (whose King Kaiser recalls Carl Reiner's Sid Caesar impersonation on "The Dick Van Dyke Show"), Josh Mostel (as a dyspeptic head writer), and David Lipman and Mary Stout (as the embarrassing relatives of any Jewish boy's nightmares) also have their scattered amusing moments. Usually these occur when Mr. Dougherty reproduces shtick from the film, most notably in the sequence in which Benjy takes Swann to his mother's home (or, as Ms. Kazan famously calls it, her "humble chapeau"). For the leads, Mr. Dougherty has written some talky emotional scenes whose prosaic quality is too often matched by Ms. Ahrens' earnest lyrical essays on the differences between pastel-hued celluloid fantasies and the harsh realities of life.

In "Once on This Island," Ms. Ahrens and Mr. Flaherty also wrote in an anachronistic style; their nominally Caribbean songs had a Rodgers and Hammerstein lilt. Here they are just as consciously evoking the brassy, competing sound of the same Broadway era, even to the point of writing a Manhattan night-life production number, complete with dancing cops and sailors and loose women, of the sort that seemed de rigueur in every musical with a New York setting from "On the Town" to "Mame" to "Annie." But this time the echoes are pale and the gaiety forced. "My Favorite Year" uncorks the intoxicating vintage of 1954 only to send its audience crashing right back into the morning-after sobriety of that less-than-favorite year, 1992.