GO FOR IT. Superman," whispers the little kid sitting next to you as popcorn butter drips from his chin to his dungarees. But on the screen, the Man of Steel is neither stopping a runaway train, nor punching out bank robbers. He's in bed with a gorgeous woman, worrying about things that have nothing to do with truth, justice, or the American way. Superman II is more than just another adventure for our favorite hero. In addition to saving the planet, and perhaps the universe, he confronts his own past, throws a dinner party for two at his North Pole bungalow, and--horrors!--exposes himself in more ways than one to Lois Lane. Superman has passed through intergalactic puberty. The Caped Wonder has come of age.

The makers of the sequel to Superman have drastically expanded their character and given depth to the world he must protect. Things used to be so simple; after a long day of reporting for the Daily Planet. Clark Kent would find out that his shapely cohort had managed to get herself stuck in a shark tank in Saudi Arabia. After checking into the nearest phone booth, he would emerge, leotards and all, leap tall buildings and so forth, to arrive at the scene of the crime just in time to save poor Lois. There would always be a moment of sexual tension and a brief query as to where the heck Clark goes everytime something happens, and then, bang-o, you would come to the end of the comic book, or the 6 o'clock news would start.

You never got much more than this in the initial movie either. But in Superman II, all of the paradoxes of the legend come unraveled. Lois finally has all of her suspicions confirmed, as Kent's pinstripes are torn away to reveal the crimson "S". Their relationship, though straightforward enough in their unmitigated devotion, is burdened with the knowledge that they must ignore a disintegrating society to find happiness in the big guy's bean bag of a bed. Superman must make coices he has never faced before, knowing that Evil has managed to trap Good in a nasty headlock while he was busy with his private life.

The result is a film far superior to its predecessor and fairly successful in its own right. There's no way you can take Superman seriously for more than two hours, and in Part I, director Richard Donner couldn't quite figure out how to make the transition from rock 'em-sock 'em plot to a little self-deprecating dialogue or visual humor. Richard Lester masters this problem early on, and with good performances from his stars, gets you to root for the good guys at the same time that you laugh at them.

That's not to say there isn't plenty of good old fashioned rough stuff in this movie. For a warm-up, you travel to Paris, where Lois has somehow gotten herself trapped in an elevator that not only has a nuclear bomb in it, but is also plummeting to earth from the top of the Eiffel tower. No job for a mere mortal. In the process of disposing of the explosive, Superman unwittingly allows the three chief villains of this saga to escape.

THE TRIO--Zod, Ursa, and Non--are none other than the criminals-in-chief of Superman's home planet, Krypton. At the end of Part I, they were imprisioned by our hero's father and doomed to float about the galaxy in a funky outer-space jail cell. Freed, they decided to take over earth and rule forever, needless to say, in a most unpleasant manner.

What follows is the requisite demonstration of power by the three meanies, who soon discover they have strength equal to that of Superman. At the White House they receive an unconditional surrender from a cowering President (who looks alarmingly like Sen. Howard Baker of Tennessee), and aided by the enterprising earth-bound villian, Lex Luthor, they set out to find the only being standing between them and a happy reign of pain and degredation.

Meanwhile, Clark and Lois are sounding each other out like a pair of high school sophomores at a kitschy Niagra Falls motel. Overwhelmed by his own super-human passion, the man with x-ray vision gives in to his partner's advances. There's only one catch--as a home movie of Supermom reminds her son later that evening--you can't mess with the locals and keep your Kryptonian powers. Don't be too quick to criticize, though; if you saw Margot Kidder in a bathrobe, you too might forget about the dire state of world affairs for a few minutes.

Kidder, who lends a provoking sharpness to the most intrepid of lady reporters, works well with Christopher Reeve to build on the relationship they outlined in Part 1. She is tough with Clark, who follows her around like a puppy, but never pretends that she could love anyone but the Superstud. Confronted by her main man, she melts like ice cream and later elarns to appreciate him even when he is reduced to the most handsome mortal hunk you could ever wrap two arms around. Reeve plays the protagonist with an appropriate blends of righteousness, courage, confusion (over how to tow in Lois without blowing his cover), and, above all else, good humor. Neither has many lines to mouth; dialogue is kept to a merciful minimum throughout.

Yet with their half-finished sentences and frustrated glances, they succeed parodying the struggle for personal fulfillment after the fall from innocence. Of the other actors, only Gene Hackman merits particular mention for his subdued portrayal of indefatigable Lex Luthor, the man who for his part in the subjugation of the world "only wants a little beachfront property--the continent of Australia."

In the end, there are a lot of silly scenes and ridiculous holes in the plot of Superman II. But somehow they don't seem that annoying. This is not a movie worthy of detailed analysis; its very frivolity is its greatest strength. And as the house lights go up and the little kid spills the remains of his popcorn on your shoes, you'll find yourself surprisingly satisfied that Superman did go for it after all.