Osmosis Jones.

About Osmosis Jones

Osmosis Jones is a 2001 American live-action/animated buddy cop action comedy film directed by the Farrelly brothers and written by Marc Hyman starring the voices of Chris Rock, Laurence Fishburne, David Hyde Pierce, Brandy Norwood and William Shatner, with Molly Shannon, Chris Elliott and Bill Murray in live-action roles. It combines live-action sequences directed by the Farrelly Brothers and animated ones directed by Piet Kroon and Tom Sito and follows the titular protagonist, an anthropomorphic white blood cell police officer (Rock), as he teams up with a cold pill (Pierce) to protect his unhealthy human host (Murray) from a deadly virus (Fishburne) he unintentionally contracted.