The moment you hear about the premise of Junior Arnold Schwarzenegger gets pregnant you can safely assume you already know every joke in the movie. Well, okay, not every joke. Early on, there's a delightful moment in which Arnold, a crusading geneticist who has had himself injected with a miracle fertility drug, runs into his devious ex-boss (Frank Langella) at a cocktail party the very boss who'd nixed further experimentation on the drug. Now, staring at Arnold with befuddled wonder, he says, ''You look radiant!'' (If only he knew why.) Langella, who has become an ace scene stealer, throws away a line like that one with perfect, quizzical gruffness; he seems to be surprising even himself as he says it. The payoff is that Arnold does look radiant he's so lit up with expectant joy he's practically emitting sunbeams.
For every joke like that one, however, there are a dozen more on the order of Danny DeVito, as Arnold's scientist partner, announcing, ''Everything's perfectly normal. Except for the fact that the mom is also the dad!'' A joke like that deserves a rim shot. Directed by Ivan Reitman, who in recent years has moved away from the scruffy anarchy of Stripes and Ghostbusters and toward human comedies with ''heart'' (Twins, Kindergarten Cop, Dave), Junior, for all its plastic gags, has been made with a tone of gentle, almost disarming sweetness. Once again, Arnold Schwarzenegger is reinventing himself, putting a deprecatory spin on his own image. Before, he learned to play his iron-butt, Teutonic machismo for laughs. Now the joke is that he winkingly emasculates himself, becoming sweet and sensitive and a crybaby i.e., the cliché image of a mom-to-be.
Schwarzenegger's willingness to flirt with femininity, to become truly ''radiant,'' is the most engaging aspect of Junior. Unfortunately, the script doesn't portray his transformation to starry-eyed pregnant bliss with much comic ingenuity. At the beginning, he's supposed to be a cold fish, a guy in need of a spiritual recharge. But we don't see much of that he just seems like a dedicated scientist and his melt into angel-eyed ''motherhood'' is complete before the plot even gets rolling. Far more effort has gone into the creation of the prosthetic pregnant bellies, which always manage to look like Silly Putty anyway.
After a while, the cozy, domestic fuzzy-wuzziness of Junior becomes inseparable from its formulaic blandness. Here's Arnold getting morning sickness, thumbing through Modern Maternity magazine, and scarfing a pickle (now that's original). Here's Emma Thompson, in I-can-let-my-hair-down- and-do-a-dumb-blockbuster mode, portraying a professor as...a klutzy space case. Who longs to have a child. And who falls for Arnold, never suspecting, even after she learns of his extraordinary condition, that she's going to have a child. And here, finally, is the climax, the payoff that no Ivan Reitman comedy can afford to be without: the hero's I'm-into-my-new-role-now montage. In this case, Arnold, in full drag, bonds with the other residents at a spa for expectant moms. As the inevitable feel-good power-schlock ballad (Patty Smyth singing ''Look What Love Has Done'') oozes onto the soundtrack, we see him doing breathing exercises, practicing motherhood with life-size baby dolls, picking wildflowers, crying with joy. This is the sequence of triumph, all right, the moment when a movie like Junior smugly celebrates the fact that it can become a hit by telling us the same joke over and over again. Arnold's eagerness to tweak his own persona remains as winning as ever. But until the day they start selling crystal balls at the concession counter, it would be hard to imagine how a movie could be any more predictable than this one. Junior, I'm afraid, is the very model of what mainstream Hollywood comedy has become: a form of high-concept pacifier. C