"BEING JOHN Malkovich" is for anyone who ever wondered what it was like to get into someone else's head -- literally.

Penned by Charlie Kaufman and directed by Spike Jonze, this brilliantly inventive fantasy fuses weird to wonderful, as John Cusack, Catherine Keener and others enter actor John Malkovich's brain by means of a "portal."

I'm talking about a small door, about waist high, that leads them into the winding pinkish tunnel of his cranium, and, eventually, Malkovich's mental control tower.

There they are, looking through his eyes as he wanders through his Manhattan apartment, takes a shower, checks his teeth in the mirror and leafs through catalogues of bathroom towels. There they are, being John Malkovich.

How do they get to this point? It starts with Craig Schwartz (Cusack), a bearded, world-weary puppeteer whose obsession with artistic integrity has him living in near-poverty in New York City.

His idea of a really good puppet show? "Abelard & Heloise: A Love Story," in which the lovelorn marionettes scratch frantically at the cloistered wall that separates them, their hips undulating in suggestive rhythms. No wonder a passing father slugs Craig in the mouth when he performs his show on the sidewalk.

"Honey, not again," says his wife Lotte (Cameron Diaz, practically unrecognizable in her unkempt scuzziness), when he returns with a bloody mouth.

Craig's marriage isn't going too well, either. Lotte, who has a menagerie of odd pets, is preoccupied with her pet chimp Elijah, an emotional wreck who wears a diaper and suffers traumatic memories of his capture by humans.

Driven to find income, Craig gets a job as a filing clerk at LesterCorp, which is located on the 7 1/2th floor of an office building.

The workers stoop constantly under the low ceiling. Their boss Dr. Lester (Orson Beane) is obsessed with juicing and sex. And Lester's "executive liaison" Floris (Mary Kay Place), who mishears every word spoken to her, assumes everyone but her has a speech impediment.

"My name is Schwartz," insists Craig, after Floris has called him Mr. Juarez.

" `My name is Warts?' " says Place.

Craig falls madly in love with fellow worker Maxine (Keener), a dour, attractive woman who has no interest in him. But that changes when he tells her of his recent discovery: a door behind some cabinets, which leads to Malkovich's gray matter.

Craig and Maxine join forces, offering tours of Malkovich for $200. Things get really complicated when Lotte visits John's inner recesses and enjoys the experience a little too much. Suddenly there's talk of "sexual reassignment surgery" and it seems that Maxine -- who works her charms on the unwitting Malkovich himself -- really likes the idea of Lotte entering John's head and indirectly participating.

Obviously, Craig isn't thrilled with this odd triangulation, which excludes him from both women. And we haven't even begun to describe Malkovich's reaction to the beeline of people entering his brain.

This movie would not have been possible without Malkovich's sporting consent. As the central object of everyone's affections, he plays himself with wonderful ironic restraint. His state of bewilderment -- especially when those unseen invaders learn to control his words, actions and even lovemaking -- is hilarious.

Cusack and Keener create an amusingly twisted synergy; she's a boho/Uptown snoot constantly looking for a better social prospect. He's a sleazy narcissist, fixated on artistic success. They're terrible for each other, which is to say perfect for "Being John Malkovich." And Mary Kay Place's few moments as Floris, alone, are worth the price of admission.

Debuting screenwriter Kaufman and Jonze, who played Pvt. Conrad in David O. Russell's "Three Kings," and who's a veteran of music videos and television commercials, have infiltrated the stagnating brain of Hollywood filmmaking and filled it with something provocative and engaging. This movie, so full of creativity, so subversive, so alive, makes the prospect of their future collaborations -- including a movie called "Human Nature" -- delicious.

BEING JOHN MALKOVICH (R, 112 minutes) -- Contains obscenity, nudity and sexual scenes. At the Cineplex Odeon Shirlington 7, Dupont Circle 5 and Avalon.