Osmosis Jones is the Farrelly brothers' idea of a family movie, and it's one that contains two scenes that I'd be reluctant to let any children of mine see (one involves upchucking, the other a pimple, and both are shown in all their perfectly reviling glory).

Bill Murray plays Frank, a zoo attendant who has allowed himself to go completely to pot, from consuming a steady diet of junk food to lax personal hygiene habits, all to the perpetual consternation of his young adolescent daughter (charmingly played by Elena Franklin), who chides him regularly but loves him anyway.

Frank, though, is actually a secondary character, the basis for the teeming City of Frank, the anthropomorphic realization of how all the myriad systems of the human body work together to keep itself functioning. Osmosis Jones is a white blood cell who talks and acts like a rogue police cop, and is assigned to work various details depending on what favor he is in at the time. He's working tartar control on Frank's gum line when a mysterious, sinister invader shows up, looking like one of the more cosmic villains in a Fantastic Four adventure. "Be careful, I'm contagious," he growls, as he extends one talon-like fingertip that causes a fissure of fiery inflammation to crack-open and explode wherever it touches. 

Lawrence Fishburne provides the perfectly malevolent voice for this character, while Chris Rock does the wonderfully cheery, get-down cadences for Osmosis, who, as in any number of cop dramas seen in recent years, gets paired up to work with an unlikely partner: Drix, a souped-up cold medication who confidently blitzes various germs and bacteria (and is voiced, in another perfect match-up, by David Hyde Pierce).

Piet Kroon and Tom Sito directed the animated sequences which depict that action inside Frank's body, and, with the exception of a couple of C.G.I. and digital effects, it is all hand-drawn and looks all the better for it. It's also more inspired, and appealing, than what's going on outside. The live-action sequences, which are filmed in a haze of brown (I suspect the usually ace cinematographer Mark Irwin was goaded along with cries of, "Use more filters! Make it look dirtier!"), seem to become more grimy and greasy-looking as the movie goes along, and they become increasingly harder to watch. Bill Murray seems to be comfortable playing-down to expectations, happily opening his mouth to show the audience whatever half-chewed debris may still be floating around in there. Chris Elliott, with long stringy hair, shows up as Frank's beer-swilling buddy, and Molly Shannon makes a couple of appearances as a school teacher whom Frank humiliated in public -- she peers at him through dorky-looking eyeglasses, scrunches up her nose, and then explodes into a tizzy of indignation and disgust. That's pretty much all that the movie requires her to do. (At least she doesn't have to launch body-slamming kicks at people, like Renée Zellweger had to do in Me, Myself and Irene, but the filmmakers still manage to find some way to work against the natural charm of their lead actress.)