Monkeybone   A 20th Century Fox release of a 1492 production. Produced by Michael Barnathan, Mark Radcliffe. Executive producers, Lata Ryan, Henry Selick, Sam Hamm, Chris Columbus. Directed by Henry Selick. Screenplay by Sam Hamm, based on the graphic novel "Dark Town" written by Kaja Blackley and illustrated by Vanessa Chong.   Stu Miley - Brendan Fraser Julie McElroy - Bridget Fonda Death - Whoopi Goldberg Organ Donor Stu - Chris Kattan Herb - Dave Foley Hypnos - Giancarlo Esposito Kitty - Rose McGowan Kimmy - Megan Mullally Medusa - Lisa Zane Monkeybone (voice) - John Turturro   By DENNIS HARVEY Giancarlo Esposito, left, and Brendan Fraser star in 20th Century Fox's "Monkeybone," based on the graphic novel "Dark Town."   A frenetic but disappointing first step into live-action terrain for admired animator Henry Selick ("The Nightmare Before Christmas," "James and the Giant Peach"), "Monkeybone" reps a weak cross between "Who Framed Roger Rabbit," "What Dreams May Come" and Ralph Bakshi's 1992 misfire "Cool World"; that is to say, it's equal parts wacky, sappy and sniggery, a PG-13 combo ill fit for any demographic. Prospect of Brendan Fraser lost in an f/x- laden fantasy landscape should pull hefty returns at first from young auds. But pic's banal romantic angle won't do much for kids, while its juvenile sexual humor seems family-unfriendly without being outre or clever enough to amuse more sophisticated viewers. Of course, a not-dissimilar mix recently scored with all ages in "Nutty Professor II: The Klumps." But that feature benefited from brand identity. Though much more promising in concept, "Monkeybone" wastes little time lowering imaginative expectations via hackneyed characters, stale/underdeveloped conflicts and puerile jokes that presumably water down the source material, Kaja Blackley and Vanessa Chong's '95 graphic novel "Dark Town." Result is passably colorful in design terms, yet consistently misses each mark -- poignance, grotesque fantasy, man-vs.-libidinous-id humor -- by taking aim at them all as broadly as possible. Fraser plays Stu Miley, an underground cartoonist on the verge of Matt Groening-like above-ground success. He's creator of what is allegedly "America's most disturbed comic strip," though the line-drawn TV pilot seg we see doesn't bear that out too well. Dubbed "Show Me the Monkey" (and designed by Don Asmussen, whose actual newspaper strips are much funnier), its jokes hinge on ye olde conflict between Man and his Best Friend -- the one located just south of the anatomical equator. "Monkeybone" is a libidinous chimp who pops "erect" from the teenage protag's pants one day, embarrassing him in front of hottie teacher and classmates, then refuses to stay suppressed. The guy can't control his "monkey," get it? Heh-heh. Yep, that's the whole concept. Heh. Pretty twisted, eh? Heh ... har ... um ... zzzzzz. Nonetheless, "Monkeybone" evidently is set to sweep the nation, though Stu, being a stereotypically nerdy/shy cartoonist and all, quails at the "crass" cash-in merchandising already being test-modeled. Fleeing a launch party with live-in g.f. Julie (Bridget Fonda), Stu suffers an accident that lands him in the hospital, comatose. While Julie maintains a weepy vigil, Stu's subconscious is yanked to "Downtown," a waystation for souls. Depending on the higher power's whims, new arrivals are either claimed by Death (Whoopi Goldberg) and sent on to the afterlife, or given an "exit pass" allowing re-entry to mortal existence. Stu's attempts to escape this not-so-scary underworld (which resembles a mildly Tim Burton-ized variation on old Sid & Marty Krofft TV shows) are variably helped and hindered by god of sleep Hypnos (Giancarlo Esposito), sexy feline Kitty (Rose McGowan) and businesslike Death herself. Stakes are raised by his sibling Kimmy's (Megan Mullally) inexplicable eagerness to unplug hospital life-support at the earliest, medically approved opportunity. While Julie -- a scientist specializing in sleep research, conveniently enough -- races to figure out a wakeup tactic, Stu is double-crossed Downtown by his own alter ego, the mischievous Monkeybone (a plush-toy-like animation voiced by John Turturro in a Chris Rock vein). Latter steals the "exit pass" Stu has already lifted himself, then heads north. No stranger to playing cartoons, Fraser has no problem making the "human" Monkeybone watchable. But his agility and invention alone can't make "Monkeybone" itself funny. Ditto "Saturday Night Live's" Chris Kattan, who pours considerable slapstick finesse into a key later role as a corpse. Indeed, "Monkeybone" is packed with comic talents flailing against feeble material: Goldberg's familiar, flippant attitude is in sore need of better supporting quips; Mullally plays a rote knockoff of her hilarious Karen on "Will & Grace." McGowan, who showed barbed esprit in the first "Scream" and "The Doom Generation," once again plays third fiddle to her much-showcased cleavage. Fonda is perhaps the least lucky of all: Saddled with a teary, oversweetened fiancee role, she alone must shoulder the film's burden of entirely bogus sentiment, a quality no less grating than the pervasive, smirky sexual humor, which is in very bad taste by family-pic standards but isn't nearly tasteless enough to tickle anyone over age 13. Juvenile pee-pee-ca-ca tenor lands well short of the genuinely outrageous "bad taste" tropes in the likes of "Scary Movie" and "Road Trip." Pic tries to play it every which way, milking the penis metaphor one minute, going oddly prudish the next, elsewhere vaguely gesturing toward "wounded inner child" psychobabble. Designwise, "Monkeybone" sports a too-many-cooks funhouse clutter that's diverting without adding up to any cogent style or atmosphere. While realism isn't the goal here, there's considerable variance in quality of effects (created by now-standard battery of multimedia design teams), rendering pic's visual "seams" occasionally as rough as its conceptual ones. Pointless in-joke cameos feature Stephen King and Harry Knowles.   Camera (Deluxe color), Andrew Dunn; editor, Mark Warner, Jon Poll, Nicholas C. Smith; music, Anne Dudley; music supervisor, Dawn Soler; production designer, Bill Boes; art directors, John Chichester, Bruce Robert Hill; set designers, Jann Engel, Hugo Santiago, Jeff Ozimek, Todd Holland, Martin Mervel, Everett Chasex; set decorator, Jackie Carr; costume designer, Beatrix Aruna Pasztor; sound (Dolby), Geoffrey Patterson; supervising sound editor, Tim Holland; sound designer, Steve Boddeker; special makeup effects, Greg Cannom; creature effects producer, Keith VanderLaan; visual effects producer, Terry Clotiaux; special visual effects, Centropolis Effects; creature effects, Captive Audience Prods., Steve Johnson's XFX; stunt coordinator, Dan Bradley; associate producer, Paula Dupre Pesmen; assistant director, Mike Topoozian; second unit directors, Peter Crosman, Dan Bradley; second unit camera, Phil Pfeiffer. Reviewed at Sony Metreon, San Francisco, Jan. 15, 2001. MPAA Rating: PG-13. Running time: 92 MIN.