BY A.J. JACOBS Dean Cain is watching videotape of himself. And even he's impressed. The actor has swung by the sparsely decorated Warner Bros. looping room to lay in some last-minute dialogue. (Example: "Lois! Lois!") And there, up on the TV, it's...it's...Superman! Cain inspects his alter ego's Metropolis- size shoulders, popping pecs, bulging biceps. In fact, Superman is looking so big, Cain figures the tech guys must have compressed the picture. "It's not squished?" Cain asks a producer. Nope, it's the real thing, he is told. "Really? I'm looking that strong?" Yes! Well, you can't blame the guy for admiring himself. After all, that 6-foot, 195-pound expertly buffed bod is at least part of the reason why Lois & Clark: The New Adventures of Superman-- ABC's Hepburn-and-Tracy take on the Superman-Lois Lane romance--has broken into the top 20 opposite heavy hitters Cybill, The Simpsons, and Mad About You. Certainly, the show would be mighty dull without large doses of Cain's whip-smart and bantering (though still slightly nerdy) reporter. But then there's his less cerebral charm: that straight-off-the-Parthenon physique. When the former Princeton football star slips into those tights to leap a tall building or wrestle a villain, you can fairly hear the heavy breathing from half the viewing population. (Unless you are among the other half too busy downloading Internet pictures of wide-eyed costar Teri Hatcher to notice.) Says coproducer Jim Michaels: "When his shirt comes off, it's worth a couple ratings points." Several hours before the dubbing, Cain is set to work on that Nielsen- friendly chest. "The gym is closed," says Cain, 29, with a grin. "But voilą!" He unfurls his hand to reveal a key. With Coke machine-size personal trainer in tow, Cain unlocks a glass door, bounces into the Warner Bros. gym, pops some Soul Asylum into the CD player, and starts grunting. His goal: 6 percent body fat. (He's now at 8 1/2.) "I'm going to get in better and better and better and better shape," he says without a smile. But wait! Don't go confusing all this testosterone and iron with superficiality. "This is only a small part of my day," he says, hinting at a split in his personality. For Cain does have two sides--sides just as distinct as, well, that fellow with a cape and his Daily Planet counterpart. On the one hand, you have the gym-bound, just-one-of-the-guys Cain. The one who got into bar fights after college, avoids the black-turtleneck set, discusses the Green Bay Packers with the crew, throws around phrases like "Hey, boss!" and chugs brewskies. This Cain will tell you, "I didn't want to be an English major because I didn't want to overanalyze s---." (He majored in history instead.) He'll tell you he hated those acting classes he took at Princeton, the kind where you worship Stanislavsky and do breathing exercises: "Be a tree? YOU be a tree." Ask this Cain what he reads, and he'll more readily tell you what he doesn't. "That self-help psychology crap...[it's] for people who are searchers." Then there's the other Cain. The one who aspires to being more than a prime- time slab of beef. The one who spends his nights pecking away at a word processor. The one with an Ivy League diploma, for crying out loud! "Going to Princeton benefited me because I can write," says this Cain. "And [that] really, really, really makes my career different from most actors'. Yes, every actor will tell you they can write. And 99.87654 percent are full of s---!" Presumably, Cain isn't. So far ABC has aired two of his Lois & Clark scripts: "Virtually Destroyed," in which Lois gets sucked into a madman's computer; and "Season's Greedings," in which a twisted toy maker peddles evil stuffed animals. "I take my hat off to him," says coexecutive producer Eugenie Ross-Leming. "He has good instincts. Sometimes he fights for what he wants. Sometimes he's flexible. But it was his script, and we did it." Last July, Cain wrote, directed, and executive-produced another show--Off Camera With Dean Cain, a fluffy, moderately well watched ABC special about the lives of Andrew Shue, Daphne Zuniga, and a handful of other stars. ("The [network] wouldn't let me use Courteney Cox because she wasn't a big name yet," says Cain. "I was like, 'You got to be kidding me!'") He's had less luck with the several film scripts he's penned, including an Airplane!-esque comedy about a woman abducted by aliens. Cain the writer echoes the opinion of many scribes when it comes to actors: "I don't like them very much.... I wouldn't be a court jester, and that's basically what happens as an actor. You're just a clown. And if you're not funny, they'll cut your head off." Nevertheless, it is as an actor that Cain will most likely break into movies. (Hey, it's better than nothing.) He's itching for the right role-- possibly in an action flick--but so far he's been surprisingly choosey. "Every day there's a new [script], twice a week there's a new deal," swears Cain, who claims he's passed on movie roles, but refuses to get more specific. "Why make a dog?" says Cain, who earns an estimated $30,000 to $60,000 an episode. "I don't need the money that badly." His workout over, Cain is outside his trailer when--whoosh!--a middle-aged woman swoops out of an Oldsmobile minivan and appears at his side. After making sure the actor remembers they met through her husband--a gaffer--she confesses to Cain that her kids are big fans. There they are in the van, peeking out the back window! "I wanted to show them I could touch Dean Cain whenever I wanted!" That said, Mom envelops the bemused but obliging star in a full-body hug. "I knew you before you were Superman!" she fairly squeals. But Superman is no longer open to other women's affections. In the Feb. 11 episode, Lois is set to walk down the aisle with Clark, the age-old Superman-as-eternal-bachelor canon be darned. "It's the greatest unrequited love in history, and it will be requited," Cain says, although it may not happen when or where you think. Heightening the suspense is a revelation from a recent episode: The action hero has never gotten any action. Or, more accurately, hasn't gone all the way. "I made that choice--it was my script," says Cain, who betrays his writerly bent by giving the character a little more history than is probably necessary. "I mean, he's been blown before, so he knows what happens." Cain has made different choices off screen. Indeed, his sex life is straight out of some prepubescent boy's sweaty 2 a.m. fantasy. Consider his dance card: At Princeton, he dated Brooke Shields ("People on other [football] teams would mess with me a little bit"). Later he squired Baywatch Barbie Pamela Anderson--now married to metal dude Tommy Lee. ("She and Tommy--it's great. Good f------ luck!") Most recently, he had a lengthy romance with volleyball-playing model Gabrielle Reece. ("Gab and I are no longer dating. End of story.") Cain guards his privacy fiercely. He bars journalists from his house in L.A. He fled Aspen this Christmas when paparazzi swarmed the slopes. And he's driven completely batty by tabloid tales. Says Cain: "I've made a couple of follow-up calls [to reporters] to say, Screw you!" The reports linking him and Hatcher are mere mosquito stings. "There's nothing spectacular to say about our relationship," laughs Hatcher. "So people make it up. The two ways to go are that we're sleeping together and that we hate each other. Both of those have been done, and both aren't true." But a tabloid story of a different stripe cut deeply. Inside Edition tracked down Roger Tanaka, Cain's biological father, who left the family before Cain was born. Cain has never met him, nor does he have any desire to: "He's never tried to get in touch with me.... End of story." (Tanaka couldn't be reached for comment.) Cain was raised by his mother, actress Sharon Thomas (Pure Country), and her second husband, Christopher Cain, the director of The Next Karate Kid and the upcoming comedy Gone Fishin'. Although Dean scored a small part in his stepdad's The Stone Boy ("I got the role out of charity," he admits), his heart took him in a more macho direction: football. A star of his high school team, Cain gained entry into the Ivy League. "His buddies would tease him about being a jock," recalls Chris Cain. "But you can't get into Princeton unless you're smart." "Princeton was the wisest choice I ever made," says the younger Cain. "I loved the professors in tweed jackets, the classrooms so classic looking." Cain is less forthcoming when it comes to his academic performance. "I did fine. I graduated," is all he'll say. Cain broke the NCAA record for most pass interceptions and, after getting his degree in 1988, got drafted by the Buffalo Bills. But a preseason knee injury squashed his sports career before it started. (Inside-joke alert: A florist on Lois & Clark was sidelined from the Buffalo Bills earlier this season by, yes, a knee injury.) Cain landed back in Los Angeles and, at the urging of his stepfather, tried his hand at writing screenplays. Meanwhile, to pay the bills, he started acting, mugging in commercials for Diet Coke and Frosted Flakes before landing a four-episode gig on Beverly Hills, 90210 as a Shannen Doherty fling. Then his agents told him about Superman. "When I first heard about it, I thought it was stupid," he says. "But then I read the script." Cain beat out several other Superwannabes, including Kevin Sorbo, who's now saving other distressed damsels in the syndicated Hercules: The Legendary Journeys. More than his Superman, though, it's Cain's take on the mild-mannered reporter that has hooked Lois & Clark executive producer Bob Singer: "Dean has managed to keep the sort of traditional Clark Kent, but make him a hipper, more caring guy." Three years into it, Cain admits that playing Superman has the occasional downside. Getting hoisted by the crane for the flying scenes is a serious pain in the hips. And Cain can't play basketball without a you're-not- faster-than-a-speeding-bullet crack. But there's one thing he's not worried about: the so-called Superman Curse. The 1950s TV star George Reeves died suspiciously from a gunshot wound to the head. Christopher Reeve recently became a quadriplegic after getting thrown from a horse. No fears, Dean? "That's the dumbest thing in the world," says Cain. "Everybody who's ever been President of the United States--except for four guys--are all dead. So you shouldn't be President of the United States because you might die?" Cain much prefers comparisons to an action hero of an earthier nature. "Harrison Ford is a hell of a role model," he says. "I love what he's done with his career and private life. You don't know dick about him. He doesn't say much. And he's extremely humble." Cain pauses, then laughs. "Reminds me a lot of myself."