Bet you never thought you'd find an epistle by Eugene O'Neill alongside a letter by Gypsy Rose Lee.

But you can find just that -- as well as letters written by and to the likes of George Bernard Shaw, John Barrymore, Groucho Marx and Tennessee Williams -- in a fascinating exhibit at the New York Public Library for the Performing Arts at Lincoln Center.

"With Pen in Hand: An Exhibition of Theatrical Correspondence" is on display in the Billy Rose Theatre Collection during regular library hours through May 22.

Among the letters is one written to Gypsy Rose Lee by her mother in which 'Mama Rose' says, "I had a dream about you and a nightclub..." The remarkable thing about this letter, according to Bob Taylor, curator of the Billy Rose Theatre Collection, is that it did not surface until a few years ago -- nearly four decades after Ethel Merman's Rose sang almost those exact words in the Styne-Sondheim-Laurents Broadway musical Gypsy.

There's also a rather intriguing correspondence between Eugene O'Neill and Lillian Gish, in which he requests her feedback on Desire Under the Elms and she comes back with some constructive criticism about one of the characters -- who O'Neill in turn defends. Then there's a letter by George Bernard Shaw to Katharine Cornell, who had written the playwright for permission to do a production of Candida. In her letter the actress had enclosed a photo of herself that so impressed the playwright that he responded, "...By the way, can you act? But if you are as beautiful as all that, it doesn't matter a whit."

"There's a little bit of the voyeur in all of us," says curator Bob Taylor.

Who's to argue? For more information, call (212) 870-1639.

-- By Rebecca Paller