OK, let’s just get this out of the way. Kristin Chenoweth is a goddess. Helen Mirren may be playing the Queen of England in The Audience, but in the Roundabout Theatre Company’s revival of On the Twentieth Century, the 1978 screwball musical, Chenoweth is the Queen of Broadway. As the magnificently vain movie star Lily Garland, Chenoweth displays the rubber-faced antics of Carol Burnett, the vocal calisthenics of Audra McDonald, the timing of Estelle Getty on Golden Girls, and the versatility and quick-change artistry of Jefferson Mays of A Gentleman’s Guide to Love and Murder.

Like Broadway stars of previous generations such as Ethel Merman, Carol Channing, and Zero Mostel, Chenoweth is simultaneously her unique self and the character she is inhabiting. Lily Garland is a volatile headliner, torn between her independent status as a film icon and her longing to return to the stage and the arms of Oscar Jaffe, the equally narcissistic impresario who launched her career and now needs her back to bolster his sagging fortunes. Derived from plays by Ben Hecht, Charles MacArthur and Bruce Millholland, the book and lyrics by Betty Comden and Adolph Green and music by Cy Coleman employ traditional musical-comedy idioms along with influences of operetta and Gilbert and Sullivan to fuel the battle between these two gigantic egos on board a Chicago-to-New-York 1930s train.

In the original production, John Cullum and Madeline Kahn (soon replaced by Judy Kaye) were equally prominent, but here the show is totally Chenoweth’s. She informs every gesture and expression with subtext in this exquisitely outsized star turn. From her first entrance, when she seems to plead with paparazzi to stop snapping her, but loving it all the while, she commands the stage. Then there’s her transformation from mousy but sharp-tongued accompanist to sizzling femme fatale in Lily’s first big break. Later, she gets to have a nervous breakdown when choosing between a Noel Coward comedy and a religious epic. I could go on and on. Suffice it say, this performance deserves a shelf full of Tonys.

Then there is the little matter of the remainder of the cast and the production itself. Director Scott Ellis sharply employs David Rockwell’s glittering Art Deco set and a dexterous chorus performing Warren Carlyle’s high-stepping choreography to keep the zany action moving at a breakneck clip. William Ivey Long’s exquisite period costumes deserve praise as usual.

Peter Gallagher, a perfectly adequate singer and actor, is not quite up to Chenoweth’s Olympian standards as Jaffe, Garland’s sparring partner and former lover. He relies too much on generalized, theatrical poses and an affected “stage” voice in the manner of John Barrymore, who played the role in the 1934 film version. As a result, the romantic connection between the two leads is not as strong as it should be. The supporting stooges fare much better. Mark-Linn Baker and Michael McGrath, as Jaffe’s long-suffering henchmen, offer just the right amount of wry commentary on the self-aggrandizing of the lead characters. Andy Karl athletically delineates the lunkheaded but gorgeous Bruce Granite, Lily’s current paramour, and Mary Louise Wilson is daffily delightful as the insane passenger Mrs. Primrose, who figures in Oscar’s scheme to finance a comeback. Marvelous as these performers and the staging are, Kristin Chenoweth is the motor that powers this train and it’s a joy to watch her drive it along its crazy track.

March 15—July 5. Roundabout Theatre Company at the American Airlines Theatre, 227 W. 42^nd St., NYC. Tue.—Sat., 8 p.m.; Wed., Sat., Sun., 2 p.m. Running time: two hours and 30 mins. including intermission; $67-$147; (212) 719-1300 or www.roundabouttheatre.org.

This review has previously appeared on ArtsinNY.com and Theaterlife.com.