Kristin Chenoweth leads ‘On the Twentieth Century’ to theatrical bliss

“They don’t write dialogue like this anymore,” a producer says, leafing through the Bible in “On the Twentieth Century.” And they don’t write musical comedies like this anymore, either. Gloriously revived by the Roundabout Theatre Company, this 1978 musical — now with sparkling turns by Kristin Chenoweth and Peter Gallagher — is a fast-paced romp. Set entirely on the 20th Century Limited train from Chicago to New York, the show — music by Cy Coleman, book and lyrics by Betty Comden and Adolph Green — barrels down the tracks to theatrical bliss. Chenoweth plays Lily Garland, the movie star whom Oscar Jaffee, Gallagher’s down-on-his-luck producer, sees as his ticket back to the big time. Having transformed her from a mousy backup pianist named Mildred Plotka into a glamorous Hollywood diva, Oscar thinks she owes him.