Call it a premature yet promising start to the summer action season. Somehow "The Scorpion King" -- a movie starring a professional wrestler and spun off from a shameful sequel -- has become the most enjoyably, unapologetically jumbo-sized popcorn flick since 1999's remake of "The Mummy," this picture's indirect ascendant.

While "The Scorpion King" aims for a considerably lower brow, it's a vast improvement on its idiotic immediate predecessor. In "The Mummy Returns," WWF wrestler The Rock had a bit part as the movie's second resurrected bad guy, an ancient Akkadian king who sold his soul to a "dark god" in order to win a war. "The Scorpion King" is that character's backstory, a tongue-in-cheek, "Conan the Barbarian"-like, 3000 B.C. adventure packed with over-the-top action and intentionally cheesy catch-phrase dialogue.

The Rock plays Mathayus, a sinewy assassin hired by the assembled remnants of several defeated tribes to kill the sorcerer who serves a powerful tyrant king that decimate their lands and peoples. Without supernatural guidance, the inexplicably interracial tribes (led by colossal Michael Clarke Duncan, "The Green Mile") believe they can defeat the ruthless, psychopathic Memnon (Steven Brand) and his silly mohawk-flattop hair-do.

What Mathayus didn't count on, however, was the sorcerer being a nearly naked babe (Kelly Hu) with a sultry disposition and impossibly pert breasts (apparently the plastic surgery business was booming 5,000 year ago). After learning the beauty has been Memnon's prisoner since childhood, Mathayus rescues her instead of whacking her, then leads the united tribes in an attack against their grandiose enemy, who rules from the spectacularly reproduced sin city of Gomorrah.

Director Chuck Russell -- who has made movies as good as Jim Carrey's "The Mask" and as bad as Kim Basinger's embarrassingly awful supernatural thriller "Bless the Child" -- wastes no time setting the unabashedly B-movie tone of "The Scorpion King" with an action-packed prologue. Mathayus rescues his brother (soon killed by Memnon) from a band of ruffians by beating them up with modified wrestling moves and firing arrows at such velocity that their targets are sent flying across the room.

That milieu prevails throughout the picture, as The Rock proves himself a charismatic and self-deprecating leading man. This guy isn't going to be doing Shakespeare any time soon, but he plays his action scenes with grunting, gung-ho gusto, his face is full of expression (he puts that famous lifted eyebrow of his to comedic use) and he can deliver a punchline with just the right ironic inflection.

"I'll kill half, you kill half," he says to a street urchin who helped him sneak into Memnon's castle as guards bear down on them. After a double-take to the boy he shrugs, "OK, I'll kill 'em all."

"The Scorpion King" pilfers ideas for its well-choreographed, humor-heavy, almost non-stop action sequences from several sources, and it lifts the sorceress's subplot straight from the James Bond movie "Live and Let Die." If she loses her virginity, she loses her powers, so when she's recaptured after a night with Mathayus, Memnon gives her a dangerous test to prove she's still chaste (which she ain't).

But like "The Mummy" before it, "The Scorpion King" is often deliberately derivative -- an homage of sorts to all its genre predecessors -- and it's never to be taken seriously. How could it be with its scenery-chewing baddies, its sissified, sniveling, snarky comic-relief sidekick (Grant Heslov in an unfortunate Arab stereotype role), and its crazy inventor crony (Bernard Hill) who conveniently comes up with the formula for gunpowder just when the good guys could use an explosion or two?

A better question might be why -- with the same writers and producers behind the scenes -- wasn't the insipid, insultingly contrived "The Mummy Returns" this much fun?