ACTING AGAINST AIDS: Arena Stage is putting on a benefit preview performance of Moss Hart's comedy "Light Up The Sky," which goes backstage to look at a group of theater folks on opening night.

The performance, 8 p.m. Thursday, will benefit Whitman-Walker Clinic's Schwartz Housing Services program, and Rap Inc.'s educational outreach and drug prevention programs.

During the last two weeks, actors from all three shows at Arena sold their home-baked and autographed cookies in the lobby at performances -- the sale raised more than $2,000 for Whitman-Walker. From "All The King's Men," Stanley Anderson baked carrot cake muffins and Halo Wines made pecan balls; Kimberly Scott of "Joe Turner's Come and Gone" offered Kahlua brownies; and "American Splendor's" Brigid Cleary made chocolate and vanilla fudge.

Also benefitting the Whitman-Walker clinic is a tribute to musical theater director/choreographer/legend Michael Bennet, by Washington actress/singer Julia Nixon. Nixon, who in 1984 played the role of Effi White in the Broadway production of "Dreamgirls," will be backed by her band Julia and Company. She will sing songs from Bennett productions and will deliver her personal reminiscences of the director.

"I got to know him quite well," Nixon says. "Michael made a habit of taking the leading performers out and talking with them. And when I lost my voice at the beginning of my run, I was sure I was going to lose the role, too. And he took me into his office, and said 'The role is yours for as long as you want it.' That's one of the sweetest things I remember about him." The benefit is Sunday, December 13, at Dakota, 1777 Columbia Rd. NW. Call 265-6600.

The always-controversial director Peter Sellars is still as cheeky as ever. Sellars, who is "on sabbatical" from the American National Theater at the Kennedy Center, recently expressed dissatisfaction with theater in general. Ironically, his pronouncements arrive just as his work is hitting New York stages for the first time.

"I learned a lot about the climate of Washington under Reagan's second term," Sellars says in an interview in the December issue of American Theatre magazine. "I suspect it may be different after Contragate, but the whole experience has made me back off from theater for a while. Theater is not a form that has much to do with the culture. It has become financially impossible and nonsensical for audiences, performers -- everyone. That's because theater is not an adequate means for describing the shape of life in America right now. It all takes place as these gestures frozen in time."

Sellars goes on to say he'll concentrate on operas and films for the next three years, but he's changed his mind before. "Zangezi," by Russian futurist Velimir Khlebnikov, was a cult hit when it played at the new Museum of Contemporary Art in Los Angeles last year, and is now playing at the Brooklyn Academy of Music's Next Wave Festival; the Sellars- directed opera "Nixon in China," a collaboration with minimalist composer John Adams, librettist Alice Goodman and choreographer Mark Morris, opens this weekend at the Next Wave Festival and is due at the Kennedy Center in March.

When cutting-edge monologuist David Cale comes to Studio Theater for two weeks of holiday performances, it will mark the first time the Studio has ever brought in an out-of-house production. "It's been important to us -- we've only presented our own work from absolute scratch," says Studio artistic director Joy Zinoman.

Zinoman first heard about Cale, who started making his name in the clubs of downtown Manhattan, last year, when her daughter Amanda, a film editor, called and said, "You've got to put this guy in Washington." "We don't do that," Zinoman said. But after Studio's season-opener "North Shore Fish" closed early because of tepid reviews and poor houses, Zinoman found herself with an empty new theater and bills to pay, and thought of Cale.

The rising star was priced out of Studio's League, Zinoman says, but fortunately, New York's Kitchen, an alternative performing arts space, has a National Endowment for the Arts grant to help support Cale's national tour. The grant will take him to the Mark Taper Forum and the Goodman and Guthrie Theaters as well as subsidize his Studio appearances.

New Playwrights' Theater was also considering importing a holiday act, "new vaudevillian" Bob Berky. The theater even sent out a press release announcing the show. But artistic director Peter Frisch suddenly had second thoughts, and the press release has been "recalled." "Berky was going to mean a tremendous outlay of money for us, and I thought 'We've already got a show in here that we're very proud of, and I want to extend it.' " So the current production of Mark Handley's imaginative "Idioglossia" will now run through December 20. Frisch is currently working with playwright Larry L. King ("Best Little Whorehouse in Texas") on the final rewrites for King's "The Night Hank Williams Died," which debuts at NPT February 3.

Michael David Fox, artistic director of Moving Target Theater, has begun a directing internship at Arena. Fox will assist Arena producing director Zelda Fichandler in the production of Pirandello's "Enrico IV," which will open at the Kreeger in January.

Former Arena company member Robert Westenberg, who is currently playing the role of The Wolf in Stephen Sondheim's new musical "Into The Woods," will play Sherlock Holmes in the seventh annual Holiday Performance, "The Adventure of the Blue Carbuncle." Actors and technicians from nearly every theater in Washington are pitching in to help put on the one-night-only event; 10 pounds of non-perishable food will get you a seat, 8 p.m. December 14 at Arena Stage.