Describe

Mollie Jensen (Kirstie Alley) is an accountant living and working in New York City. The latest client she has been assigned by her firm is a charmingly handsome but shallow, womanising executive named Albert (George Segal). Albert seduces her, and although he is married, he embarks on an affair with Mollie, promising to leave his wife for her.

Mollie insists that their relationship has to stop; however, succumbing to temptation, she proceeds to have sex with him, and becomes pregnant. Once she realizes this, Mollie informs Albert, who takes the news well and again promises to leave his wife and raise the baby with her. Until then, Mollie decides to tell her eccentric and over-bearing parents (Olympia Dukakis and Louis Heckerling) that there is no father and that she became pregnant via a sperm donor.

Mollie continues her relationship with Albert as the pregnancy develops; however, she fears he's seeing another woman, Melissa (Joy Boushel).

Later, when Mollie and her best friend, Rona (Twink Caplan), are shopping, Mollie finds Albert in a clinch with Melissa. Angry and upset, a heart-broken Mollie storms off in a rage while the fight causes her to suddenly go into labour. When she hails a cab, the driver, James Ubriacco (John Travolta), realises the seriousness of the situation and speeds off wildly to the hospital. Upon reaching the hospital, the nurses mistake him for the father of Mollie's baby, and he feels inclined to stay. Mollie gives birth to a son she names Michael, or "Mikey" (voiced by Bruce Willis and played by child actors Jason Schaller, Jaryd Waterhouse, Jacob Haines, and Christopher Aydon).

A few days after Mikey is brought home, Mollie receives a visit from James, and he returns the purse she left behind in his taxi. James meets Mikey, and they seem to enjoy each other's company.

Over the next month or so, Mollie is dealing with being a single parent and Mikey is becoming used to his new world when she discovers that James has been using her address to keep his grandfather (Abe Vigoda) in a nursing home in the local area. She confronts James and he offers to babysit Mikey if she lets him continue to use the address, which she agrees to.

Mollie starts dating again but quickly realises that none of the men she has been seeing are good enough for Mikey. One night, she lets her guard down and almost sleeps with James; however, after imagining what life would be like if she married him, she asks him to leave, despite James telling her he loves both her and Mikey.

Soon after, Mollie is forced to help Albert with his taxes, when he pleads with her to let him see Mikey (who he mistakenly calls "Mickey").

Mollie agrees to let Albert see Mikey that night but forgets to inform James, who is babysitting Mikey. A fight ensues when Albert arrives and claims to be Mikey's father; James does not believe this is possible, as Mollie had told him that Mikey was conceived by a sperm donor. James and Mollie get into an argument, and he leaves.

Later, Mollie takes Mikey to see Albert, who shows that he has not changed; she proceeds to destroy his office with the help of a very enthusiastic Mikey.

Mollie later receives a call from the nursing home James's grandfather is staying at complaining about his behaviour. She explains to the manager why James's grandfather's behavior had been so bad, and the manager agrees to let him stay, believing Mollie to be James's wife. Mollie runs into James outside the office; he had overheard discussion, and he thanks her.

After Mikey sees a yellow taxi cab outside the nursing home and believes it to be James, he proceeds to leave and ends up standing in the middle of open traffic, looking for James's taxicab. James and Mollie rescue Mikey from the street, and when Mikey calls James "Da-da," Mollie sees that James is not only perfect for Mikey, but perfect for her, as well. They kiss, with Mikey looking on happily.

As the credits roll, an older Mikey and James are shown walking through a hospital to see Mollie (now married to James), who has just given birth to Mikey's half-sister, Julie, setting the sequel, Look Who's Talking Too, in motion.