Broadway insiders Ben Hecht and Charles Mac-Arthur (creators of The Front Page) supply the zippy dialogue for Twentieth Century, Howard Hawks' screwball classic about the clash of two zeppelin-size egos. John Barrymore plays Broadway impresario Oscar Jaffe, a comic variation on Svengali whom he portrayed in 1931 (the witty script even pays homage to it). After transforming Carole Lombard's lingerie model, Mildred Plotka, into theater star Lily Garland and becoming her lover, Oscar drives her away with his possessiveness; Barrymore lets us glimpse the dangerous side to Oscar even when his behavior is hilariously over the top. Without Lily, Oscar's career derails. A chance for reconciliation arises when he and his ex, now a chinchilla-clad Hollywood diva, wind up on the elegant train of the title en route to New York City. But the zanies on board a religious loony, the Oberammergau Passion Players, Lily's boy toy complicate Oscar's plans. And though the insults (''you foul Corsican'') and argot (''I'll cool you off in 17 shades of lavender'') reach exhilarating heights, the comedy is about possession more than romance, and the acid ending reflects a bracing sophistication. While Lombard is superb (declaring between fits of pique, ''I despise temperament!''), Barrymore steals the laurels, whether he's tossing his Byronic looks in outrage or imitating a camel chewing its cud.