Look Who's Talking

Mikey: So they come in different sizes? What are these? Jumbos?
James: Are you thinking what I'm thinking?
Mikey: Yeah. Lunch!

Mollie Jensen (Kirstie Alley) is an accountant living in New York City. She's been having an affair for quite some time with a wealthy client, Albert, who continuously makes excuses for why he hasn't left his wife yet. Mollie ends up pregnant, and Albert promises to support both her and the baby.

But then, she finds Albert with another woman. The shock sends her into labor, and she is forced to take a cab driven by James Ubriacco (John Travolta) to the hospital. James is a nice guy, sticking around and providing support all through the birth. A few days after, he shows up at her apartment to return her purse, which she had left in the cab. He immediately hits it off with Mollie's son Mikey (voiced by Bruce Willis). Eventually, a relationship develops between the two adults, with baby Mikey commenting on it all the way.

Let's face it, the real appeal is not in the romantic comedy plot line, but the fact that this time, we get the baby's POV on the matter. For the most part, it's Actually Pretty Funny.

Followed by two sequels, with diminishing returns. Also spawned a short-lived Spiritual Successor sitcom, Baby Talk, which ran for two seasons from 1991-1992. While the sitcom was a different continuity and none of the film's characters appear, the characters were created by Amy Heckerling, who wrote and directed the first film.

Tropes used in Look Who's Talking include:

Bad Date - Molly has one, thanks to a "little helpful advice" from James to her date.
But We Used a Condom - Mollie has a diaphragm, it just doesn't seem to do her any good. (Considering it's one of the least reliable methods of birth control, probably right behind "pulling out"...)
Chekhov's Gun: When James first visits Mollie after she gave birth to Mikey, he returns her purse, which she left in his cab while in labor. He mentions her diaphragm was inside. In the second film, James and Mollie conceive Julie despite the fact that she was wearing that diaphragm.
Deadpan Snarker - Lots of Mikey's commentary falls into this.
Double Entendre - The entire scene when James is taking the splinter out of Mollie's hand and her mother hears outside the apartment door. Made even better when James zips his pants as he walks out.
Heel Realization: Played with in the third movie. Molly and James are both having dreams about their spouse being unfaithful... only for their dream-selves to notice each other, realize that they're being out-of-character in the dreams, and reconcile.
Imagine Spot: Several.
Innocent Inaccurate - Mikey is prone to these (being an infant and all). He thinks boobs are only there for food, for example. (Which, while technically true, is not effectively true.)
Infant Immortality - When Mikey wanders out into a busy New York City street, cars rush past him and crash all around him. He doesn't have a scratch.
- Though at least Jimmy and Molly are both astounded by this rather than taking it as a given.
Instant Birth, Just Add Water - Subverted, but Jimmy believes the trope to be true. Jimmy starts driving like a mad man when he finds out his fare (Mollie) is in labor. She yells at him to calm down and drive safe, the first stages of labor can take hours. He replies that the traffic in that area of town can take hours as well. Mollie was right, they get to the hospital in plenty of time.
"Jump Off a Bridge" Rebuttal
Law of Inverse Fertility - Mollie never plans her pregnancies.
Morning Sickness - Mollie's first clue to her conception.
My Biological Clock Is Ticking: Turned into a Visual Pun at one point, with Molly actually dangling off a massive clock hand.
My Name Is Not Durwood: Albert keeps calling Mikey "Mickey".
Nightmare Fuel - Mr. Toilet Man
Reindeer Aren't Real - Somewhat averted in Look Who's Talking Too. Baby Mikey is sitting awake at night scared. He lists various things he's worried about, and that they aren't real. This includes monsters, ghosts, witches, and dinosaurs. He knows that one of them used to be real, but can't remember which. Justified, since he is a baby.
Sequelitis: The first movie's unique twist and fantastic cast made it a huge hit. The twist was obviously less unique for the second movie, plus you now had to listen to Roseanne Barr's shrieky voice the entire time. By the third the concept was simply worn thin, with most people probably only tuning in because they had an interest in the family's storyline.
Straw Character - Molly's brother, representing everything a New Yorker should not believe.
You're Drinking Breast Milk- Jimmy does a Spit Take when Mollie informs him the bottled milk he put in his coffee is her breast milk.

Jimmy: Why didn't you tell me?
Mikey: Hey, you're on your own.