Sigourney In 3-D

“If someone had a gun to my head and said, ‘Define yourself,’ I’d have to just start by saying, ‘I’m a New Yorker,’” said Sigourney Weaver. “Whatever that means.”

The 57-year-old actress was waxing poetic about her city of birth and current residence last Friday from 2,500 miles away in Los Angeles, where she had just completed a press junket for one movie and put in a few days work on another, the highly—highly—anticipated James Cameron project Avatar, his first major film since 1997’s box-office- and award-gobbling Titanic.

Avatar, which Mr. Cameron has been developing for the past 11 years, isn’t slated for release until 2009, and beyond a handful of specifics—the plot has something to do with a battle against a far-away planet’s inhabitants; it will employ groundbreaking C.G. techniques; and it will screen only in 3-D theaters—not much else about it is known. Ms. Weaver confirmed that she wasn’t really allowed to discuss the film. “But even if I told you, it’s still very hard to understand what they’re doing,” she said. “It’s so virtual. It’s very exciting. Someone was on the set yesterday and was asking me what the difference is between doing something like this and doing something like Aliens. And you know, Aliens had things you can see and touch. There was a lot of steam,” she laughed. “We didn’t have anything like this.

“I thought it would be surreal,” she continued. “But, in fact, for actors, an empty stage that sort of represents a planet and things like that, it’s easy to imagine for us. We’re so used to being on an empty stage and imagining it’s some drawing room or whatever. It’s fun! It’s like going back to Off Broadway.”

BORN SUSAN ALEXANDRA WEAER (SHE CHANGED her name to Sigourney after reading The Great Gatsby at age 14), she attended the tony Brearley School, Stanford University and the prestigious Yale Drama School (along with Meryl Streep). She made her first on-screen appearance in the most New York City of all New York City movies, Annie Hall (paying Alvy’s movie date and clocking in about six seconds of screen time). But it was Ridley Scott’s 1979 Alien, followed by Mr. Cameron’s equally successful follow-up, Aliens, that made Hollywood sit up and take notice of this unusual beauty. In her handsome face, Ms. Weaver managed to radiate both intelligence and class. She was also possibly the first woman who made plain cotton underwear downright sexy.

The consummately elegant actress, as at home on a bare stage as she is in front of a green screen, has been able to maintain a fine balancing act throughout her career. She mixes up mainstream movies with indie projects and theater; it’s all heavy dramas one moment, lighthearted comedies the next. Has any single actress been so winning in every single genre? Just a few of her numerous film credits include: The Year of Living Dangerously, the Alien trilogy, Gorillas in the Mist, The Ice Storm, Death and the Maiden, Ghostbusters, Working Girl, Dave, Tadpole and Heartbreakers. She has appeared in plays equally as varied, including Hurly Burly, The Merchant of Venice and Mrs. Farnsworth.

This year offers a perfect snapshot of Ms. Weaver’s career M.O.: She has two wildly different independent movies coming out within weeks of each other, a play that begins public previews in May, and—in between—a few trips back to L.A. to put in time on James Cameron’s $200 million blockbuster. “I think it’s fun to mix it up,” she said. “It’s an intentional choice. I started in New York doing Off Off Broadway, and I love doing smaller, more intimate projects that are a little more out there. I find that independent film is the perfect reflection of my love of Off Off Broadway. The fun is to balance two excellent small films like Snow Cake and The TV Set with a monster project like Avatar. I really feel like an actor when I get to go back and forth between these different worlds.”

First up is Jake (son of Lawrence) Kasdan’s The TV Set, in theaters April 6, a hilarious peek-behind-the-curtains look at network pilot season (which is akin to seeing how sausages get made) starring David Duchovny. He’s shaggy, bearded and believably neurotic as a writer-director type trying to shepherd his show onto prime time without losing his dignity. Ms. Weaver plays his foil Lenny, the head of the network, who unblinkingly delivers lines like “I’m between marriages” and “Suicide is depressing to like 82 percent of everybody” and is mostly just excited about her network’s latest reality hit, Slut Wars.

It’s enough to make anyone with exposure to real-life television machinations go running for the hills. “I’m afraid I did a rather evil thing,” Ms. Weaver said with a laugh. “I invited some of my writer-director friends to the premiere, and I think it was quite upsetting for them. It was like watching a car wreck or something.” The role of Lenny was originally written for a male actor who had to drop out due to scheduling conflicts. “You know, a lot of these roles are so well-written that at this point in our culture, it can be played by a man or a woman. I thought it would actually be funnier played by a woman, because it’s funny that it’s a woman that’s obsessed whether women’s breasts are real or not,” she laughed. “We had this idea that, with women’s lib, having women in important executive positions would humanize the world. This has not panned out.”

(Of course, the world of television is one that Sigourney Weaver was born into—literally. Her father, Sylvester “Pat” Weaver, was the president of NBC in the 1950’s, and among other innovations, like creating The Today Show, is credited with establishing many operating standards still in use today. “I have to say, I have twinges of guilt playing what is his polar opposite,” Ms. Weaver said of Lenny. “He was always trying to trick people into seeing things that were good for them.”)

April 27 will bring the IFC release of Snow Cake, a small, poignant film co-starring Alan Rickman, in which Ms. Weaver tackled the challenge of playing a high-functioning autistic woman. She spent close to a year preparing. “I really needed it,” she said. “I thought I knew a little about autism, but I really didn’t know anything …. Everyone was so generous. I think it’s because there’s this great desire in the A.S. [Asperger’s syndrome] community to have more out in the world than just Rain Man, as good as Rain Man was.”

“I always base it on the story,” she said of her projects. “I just try to find a story that I would want to see, and that I’d want to be a part of it. I’m not concerned about the part—I figure, if you give me some time, I can work with that.”

MS. WEAVER CONTINUES TO LIVE IN NEW YORK with her 16-year-old daughter, Charlotte, and husband of 23 years, Jim Simpson, who runs Tribeca’s Flea Theater. He’ll be directing her in the Playwrights Horizon’s production of the A.R. Gurney play Crazy Mary.

“It’s wonderful,” she said, “to actually germinate this play and have it grow over a period of weeks, and then grow every night with a different audience—because the audience teaches you what the play is about in a different way. You don’t have that luxury in a movie theater.”

It will also be wonderful to be working at home. “I love New York,” she said. “There’s so many different things going on, and everyone thinks what they’re doing is the most important thing. It’s sort of a clash of different worlds.

“Sometimes I tell people I grew up here, and they go, ‘I don’t know anyone else who grew up here!’ But it’s a great place to grow up. It’s a wonderful place to grow old.”