Junior

No one can touch Ivan Reitman’s record for turning high concepts into popular entertainment — really popular entertainment. His latest, the pregnant-man comedy “Junior,” is no exception. What separates this straightforward chuckler from the pack is its shrewd reliance on character rather than plot, and that human dimension proves surprisingly poignant. Commercial response should result in the seasonal box office crown.

The accent is on the outrageous, and all involved get away with murder, artistically speaking. It’s a potent package and, if it can sustain in the marketplace, could well go on to the worldwide heights of last year’s “Mrs. Doubtfire.”

In a cloistered lab on an ivy-shrouded campus, researchers Dr. Alex Hesse (Arnold Schwarzenegger) and Dr. Larry Arbogast (Danny DeVito) have been working on a “wonder” drug for safer pregnancies. It’s a potential gold mine and a boon to women. But the FDA concludes that it’s not quite ready for the marketplace. So, faster than you can say loss leader, the duo get turfed and top Brit cryogenicist Dr. Diana Reddin (Emma Thompson) is ensconced in their former digs.

What’s disturbing to Arbogast is the small fortune he’s personally committed to the project and that a Canadian consortium is ready to bankroll him and the drug dubbed Expectane. What would really cement the deal is data from a human guinea pig.

The level of desperation is so high and the stakes so great, Arbogast fast-talks Hesse into being that test case. All Al has to do is carry the egg through the first trimester. It’s preposterous … but it’s for science.

“Junior” harks back to “Bringing Up Baby” rather than to past attempts with like material such as “Rabbit Test.” It’s intrinsically funny to watch serious, sober scientists involved in totally goofy pursuits.

The plot turns on one very subtle factor — hormones. The female hormone estrogen that Alex is compelled to take with Expectane may or may not be the reason he refuses to abort after 90 days. Diana needs no chemical stimulant to induce her progressively gooey sentimentality.

It’s tough to top the casting of Schwarzenegger. Who expects to see the Terminator getting in touch with his female side? Reitman delights — as he did in “Twins” and “Kindergarten Cop”– in sending up Mr. Mooscles’ persona, and Schwarzenegger’s performance is relaxed and assured.

The picture also affords Thompson the opportunity to poke fun at her prim, proper image. Not quite kooky but certainly scatterbrained, her character is a bit of an emotional and physical klutz. Her pairing with Arnold seems unlikely, but it’s obvious the two performers reveled in the challenge. DeVito and Frank Langella (as the villainous department administrator) nicely round out the cast, albeit in familiar roles — the compulsive salesman and the slick hit man, respectively.

Reitman has an unfussy visual style that at its worst emulates the flatness of television sitcom, complete with inane musical accompaniment. But his sense of storytelling is keen and breezy and his instinct about laying it on with a trowel or tossing it off in sublime fashion is virtually unerring. “Junior” is certain to spawn a lot of laughs and a lot of dough. It’s simple and clever and satisfying — an entertainment trio indeed rare, and highly appreciated.