Ephron has done her best to trivialize the feud, which began in 1979 when novelist McCarthy attacked Hellman on Dick Cavett's television show, saying everything novelist-playwright Hellman wrote was a lie, including "and" and "the." But trivial can be funny, and "Imaginary Friends" is a hip hoot that should not be missed by anyone who loves literature or the theater.

The theme of the show, actually a play with music by Marvin Hamlisch and lyrics by Craig Carnelia, is summed up when two song and dance men called Frankie Fact and Dick Fiction perform a vaudeville turn (choreographed by Jerry Mitchell) with straw hats and canes and Hellman and McCarthy dressed in Fanny Brice "little girl" costumes sing to life-size rag dolls, their imaginary friends.

Nothing on Broadway this season can match the comic fireworks touched off when two Tony Award-winning actresses -- Swoosie Kurtz as Hellman and Cherry Jones as McCarthy -- are rubbed together for two abrasive hours at the Ethel Barrymore Theater. Actually this is longer than the writers ever spent together, since they met only casually on two occasions, once when McCarthy was a student at Sarah Lawrence College and Hellman was a visiting celebrity.

This scene is dramatized because McCarthy, an anti-communist, accused Hellman, a Stalinist, of lying about novelist John Dos Passos turning against the Loyalists in the Spanish Civil War, thereby incurring Hellman's resentment and initiating the feud. When McCarthy made the same sort of accusation on the Cavett show 31 years later concerning Hellman's memoir, "Pentimento," Hellman sued her for $2.25 million.

Hellman didn't live long enough to see the slander case come to trial, but she had the gratification of watching McCarthy, whose career was in eclipse, virtually bankrupt herself paying lawyers' fees for preparation of her defense. She planned to prove that Hellman had lied in "Pentimento" about her heroism in saving Jews from the Nazis in Austria by stealing the life story of American-born Resistance leader Muriel Gardiner.

Gardiner, played straight and with touching dramatic simplicity by Anne Pitoniak, takes the witness stand to tell how Hellman had approached her about keeping quiet concerning her plagiarism of Gardiner's wartime experiences. It's a scene that never happened in real life, but Ephron's audacity in writing it pays off by giving "Imaginary Friends" the gravitas needed to balance vaudeville silliness.

Kurtz looks nothing like the plain but imposing Hellman, but Jones is pretty like McCarthy though built on a larger scale. Kurtz is a master of comic innuendo and vulgarly bitchy expression, fashionably delivered, whereas McCarthy is always the lady despite her command of acid put-down. But there is never any doubt about which of the "highbrow" writers is the superior woman -- McCarthy, who turns fact into fiction, not Hellman who duplicitously transformed fiction into fact.

The only other member of the 11-person cast, mostly appearing in multiple roles, who is worth mentioning is the redoubtable character actor, Harry Groener, who takes on the roles of the drunken mystery writer Dashiell Hammett, Hellman's lover, critic Edmund Wilson, one of McCarthy's husbands, and English poet Stephen Spender. He's good at all these impersonations, ranging from maudlin to manipulative to confused.

Hamlisch's score is music hall-inspired and nothing to write home about, although catchy at times. Carnelia's lyrics tend to doggerel -- which is, after all -- the poetry of burlesque. Director Jack O'Brien, fresh from the triumphs of "Hairspray" and "The Full Monty," has brought his full talents to bear on this show, which is full of dramatic surprises played out against a battery of vaudeville footlights.

Michael Levine's scenic design is limited to a lot of red curtains, an overhanging fig tree, some glimpses of house entrances and stoops, and odd pieces of wicker furniture, possibly to provide more budget money for Robert Morgan's tres chic costumes. Morgan has made Kurtz into something of a clothes horse to show that she is the more financially successful of the two writers.

Ephron, who wrote the witty screenplays "Heartburn," "When Harry Met Sally," and "Sleepless in Seattle," shows definite talent for fashioning an offbeat play that defies category -- a comedy with a serious theme and a play with music that isn't a musical.

Broadway needs more entertaining material like "Imaginary Friends," so let's hope Ephron will be back again soon with a second play.