The Bachelor's Baby (1996)

Jake Henry, freewheeling product reviewer, is surprised one night when Jamie appears on his doorstep with a baby she claims is Jake's. When Jamie can't care for Zack, Jake volunteers for daddy duty, despite his ignorance of childrearing and the hostility of Zack's social worker. Jake rapidly discovers that his entire life revolves around his newfound son...and that he likes it. But when Jamie wants Zack back, will Jake be able to give him up?