Out of This World : A NEW ALIEN LIFE FORM EMERGES ON NBC

John Lithgow describes himself as an “extravagant, over-the-top” actor. “Even in the most serious roles, I go the entire nine yards.”

In his latest project, “3rd Rock From the Sun,” the Tony and Emmy Award-winner goes the entire nine yards and then some. The goofy sitcom, premiering Tuesday on NBC, is the creation of the Emmy Award-winning husband-and-wife team of Bonnie and Terry Turner (“Saturday Night Live,” “Wayne’s World”).

“3rd Rock” chronicles the experiences of four brilliant aliens sent to earth to observe human behavior. Lithgow plays Dick Solomon, the brutally honest alien high commander who takes a job as a college physics professor and finds himself suddenly filled with sexual feelings for his co-worker, Dr. Mary Albright (Jane Curtin). Solomon’s “family” consists of Sally (Kristen Johnston) who is frustrated by her role in society as a woman; Harry (French Stewart), the quirky inquisitive one, and Tommy (Joseph-Gordon Levitt), the group’s elder who is now an oversexed teenager.

“It’s very liberating to be an alien,” says the easygoing actor during a lunch break in his cozy dressing room. “There are no limits on what you can do. I have always said as a character actor you pay attention to what you see among people. People behave so wildly that half the time you see human behavior that you couldn’t possibly duplicate in a play because no one would believe it. Extreme human behavior liberates you as a character actor. By the same token, I can never be too big [as an alien].”

The former Oscar nominee for “The World According to Garp” and “Terms of Endearment” throws himself into his comedic role with reckless abandon, especially in an upcoming episode in which he finds himself attracted to a student and decides to make himself look younger.

Despite his apparent ease with being the clown, Lithgow acknowledges he’s fighting the “self-protective instinct which I have as an actor. I’m always fighting against it. I’m always saying you are doing your best work when you are doing the work you never dreamed you would have the courage to do. I consider Michael Richards [Kramer on “Seinfeld”] one of our great comic geniuses because of his marvelous sense of his own ridiculousness.”

In the 13 episodes of “3rd Rock” taped, Lithgow says, “we have achieved such hilarious scenes of comic misunderstanding between aliens and human beings. My whole comic relationship with Jane Curtin is just delightful.”

Curtin, though, wasn’t in the original pilot. “We re-shot the pilot having decided we really needed a very strong human comic presence, a romantic opposite for Dick,” Lithgow explains. “Someone who could give it out and dish it out. We are both a little bit alike--we both appear perfectly normal and then we spin out.”

Lithgow acknowledges that audiences probably will be surprised to see him in such a slapstick role. But he adds, “even in my most serious roles they had a quirky spin to them. ‘Raising Cain’ certainly had comedy in it. ‘M Butterfly’ was a very funny show, but you think of those as my most serious things. I love the sound of an audience laughing. I love the sort of surprise of laughter.”

Though “3rd Rock” is a comedy, Lithgow believes it has a deep emotional core. “It appeals to me because at the heart of it is a lot of thought,” he explains. “One of the most comic speeches I have had is when I’m having a parent conference with the faculty of the high school where Tommy has to go. It’s a very funny scene because of the comic misunderstanding.

“I throw a big fit. I say, ‘Why is my son all of a sudden my responsibility? You are the ones who are supposed to be educating him.’ I throw out the line, ‘Knowledge is the only chance this planet has for survival.’ The speech goes on perfectly wild, but it paints this almost grim piece of truth. We’re doing an episode this week about death, where Dick contemplates death. No question we are after comic pay dirt, but we’re using the same stuff we use in the darkest drama.”

Lithgow had no intention to doing a TV series when he met the Turners for breakfast two years ago. “They were old acquaintances from hosting ‘Saturday Night Live,’ ” he says. “I just went and had breakfast with them to indulge them, really to see them again.”

But it turned out to be a power nosh. Accompanying the Turners were the series’ prolific executive producers Marcy Carsey and Tom Werner (“Roseanne,” “The Cosby Show,” “Grace Under Fire”).

“I hadn’t realized it was such a big deal,” Lithgow says, laughing. “I was flattered by that. I thought it was just such a wonderful premise that could go on forever in all kinds of directions. Bonnie and Terry are among the most delightful, down-to-earth people I have met in the business. Smart people who really believe in diving into the deep end of pop culture, but doing something ambitious and pushing the edge of the envelope. It just appealed to me enormously. I haven’t turned back. It’s really been delightful. And in its way, it’s the most creative work I have done.”

“3rd Rock from the Sun” airs Tuesdays at 8:30 p.m. on NBC.