The latest items up for auction at the July 11 Bay Street Theatre Summer Gala Benefit include signed items by Julie Andrews and "X-Files" stars David Duchovny and Gillian Anderson. Andrews, the mother of Bay Street Co-Artistic Director Emma Walton, will personally sign for the top bidder a piece of Mary Poppins animation art titled "Tea Time with Mary." The artwork will be part of a silent auction.

Also on the block will be a script from the television series "The X-Files," signed by Duchovny and Anderson. Other items include a five-day vacation at the new Four Seasons Resort on the island of Kuda Huraa in the Maldives, tickets to the taping of TV's "Spin City," and a private portrait sitting by Robby McDowell.

Co-starring roles with Cabaret star Alan Cumming and film star Robert DeNiro are in the offing at the "fantasy auction." Well, not exactly co- starring: the highest bidders at the benefit fantasy auction could win the chance to dance with Cumming on stage at the Broadway revival of the Kander & Ebb musical or be a walk-on in DeNiro's upcoming film Flawless.

Film stars Alec Baldwin and Kim Basinger, who are also husband and wife, will host the Bay Street Theatre's Summer Gala Benefit. The event will be held under a tent on Long Wharf in Sag Harbor, Long Island, N.Y.

The theatre promises cocktails, a sumptuous dinner provided by Sagaponack's Loaves and Fishes, and dancing to the sounds of the Peter Duchin Orchestra. Proceeds will support the theatre's many ventures, including its mainstage productions. Tickets range from $195-$500. For information, call (516) 725- 0818. Baldwin and Basinger are Hamptons habitues. Baldwin has occasionally graced the stage, most recently in this past season's Public Theater production of Macbeth. Basinger is known primarily for her film work and won an Oscar this year for her performance in L.A. Confidential.

-- By Robert Simonson