Lots of actors have assumed the rule of defender of planet Earth. But no one's taken it so seriously or wrung so many laughs from it as Tommy Lee Jones.

From the moment he relieves a band of INS agents who, unbeknownst to them, have an interplanetary alien in their midst, until he retires himself with a blast from his mind-numbing "neuralizer," Jones does what no other actor in Hollywood could do: A letter-perfect parody of Tommy Lee Jones.

The letters: MIB, Men in Black.

Men in Black is the rarest of things: a big budget sci-fi spoof that delivers on its promise, in large part because its creators, director Barry Sonnenfeld and writers Ed Solomon and David Koepp, devote as much of their time, energy and resources to plot and dialogue as they do to special effects.

The storyline, which is both simple and complex, goes like this: Agent Kay (Jones) works for a government-established-but-entirely-independent agency (MIB) which monitors the whereabouts of 1,500 or so intergalactic aliens on Earth. Their mission is to see to it that the aliens live relatively normal, peaceful lives -- and that the rest of the world's citizens don't find out about them.

That task is complicated by two simultaneous occurrences: the retirement of Kay's partner and the arrival of a "bug," an insect-like alien (Vincent D'Onofrio) who takes over the body of an upstate New York farmer named Edgar.

So Kay has the twin tasks of tracking down an interplanetary cockroach intent on starting an intergalactic war, and breaking in a streetwise but alien-ignorant agent, Jay (Will Smith), whom Kay has just recruited from the NYPD.

The result is that Men in Black is sort of half Invaders, half Dragnet, with the two parts constantly playing off one another. Witness Kay's initial interaction with a key witness, Edgar's wife, who is convinced an alien has taken over her husband's body.

"You here to make fun of me, too?" says the wife, fresh from an interview with a supermarket tabloid reporter.

"No, ma'am," says Kay, posing as a federal agent. "We at the FBI do not have a sense of humor we're aware of." Jack Webb couldn't have said it any better. And he couldn't have made it funny.

Smith has his moments, too, as the wisecracking sidekick intent on making every rookie mistake in the book, starting with an usual method of delivering a baby alien on the New Jersey Turnpike ("It's a ... a squid") and continuing with his pursuit of a deputy medical examiner (Linda Fiorentino) who may or may not like her men more dead than alive.

It would be easy to fault Men in Black on any number of scores: It's lightweight, it lacks ideas, its characters are about as deep as their disguises. Easy to fault, that is, if you can stop laughing long enough.

[ by Miles O'Dometer ]