Plot

A grown-up woman who kept her childish instincts and behavior starts working as the nanny of an 8-year-old girl who actually acts like an adult. But everything ends right-side up.

In New York City, Molly Gunn is a spoiled, wealthy, immature young woman who lives as if she were a fairytale princess. Her father, a popular rock guitarist, died in a plane crash with her mother when she was little. In a nightclub on her birthday she meets Lorraine "Ray" Schleine, a nasty young girl with an adult attitude, who lives with her careless mother and a terminally-ill father in a fancy uptown apartment. When Molly's accountant vanishes with her US$ 100,000,000.00 inheritance, she is left with nothing but debts and must work to survive--with no previous experience or marketable skills. She is hired to be Ray's babysitter, and their close contact makes Molly reach maturity and Ray act like the 8-year-old she is.—Claudio Carvalho, Rio de Janeiro, Brazil

Molly Gunn (Brittany Murphy) is a carefree and fun-spirited girl, living like a princess in a fairy tale. Her father was a popular rock-and-roll guitar player, who died in a plane crash with Molly's mother when she was a little girl. On her birthday in a nightclub, she meets Larraine "Ray" Schleine (Dakota Fanning), a hypochondriac and uptight young girl in a bathroom. Ray turns out to be the daughter of Roma Schleine (Heather Locklear), a well-known record company owner.

There she also meets an ambitious Australian singer Neal (Jesse Spencer), who is trying to get Roma to sign him a record deal. Molly immediately falls for him and invites him to her apartment after the party. When at her apartment, Molly shows an amazed Neal the collection of guitars that her father left behind when he died. Bored by Molly's strange behavior, which includes owning a pet pig named Mu, eating Pez, speaking French, and various other oddities, he eventually leaves her for his career, but she does not give up on him.

When Molly's accountant vanishes with her US$100,000,000 inheritance, she is left with nothing but debts, and she needs to find work in order to survive. But she has no previous experience or skills. She moves in with her best friend, Ingrid (Marley Shelton), who tells her that in order to stay with her, she must find a job. She is hired to be Ray's babysitter. Ray, as it turns out, lives in a fancy uptown apartment with her mother, who is too busy with work and clubbing to pay attention to her. Ray's father is in a coma, and under the care of a private nurse in the apartment. Ray doesn't seem fazed by her father's state at all. When they first meet, Ray is extremely rude towards Molly and disapproves of her carefree attitude and tardiness. The two get in a fight while they wash the dishes, which leads to Molly attempting to leave the apartment.

She is stopped by Ray, who says "When you work for me, you leave when I say you can leave". Molly informs her that she in fact doesn't work for her; that she is employed by her mother. Ray responds by saying that because of Roma's work schedule and Molly's status, she is technically working for her. Molly yells that she quits, and angrily storms out of the apartment, giving herself a bloody nose as she slams a swinging door.

Ray attempts to maintain order in her life by stifling her emotions - she often quotes Mikhail Baryshnikov: "Fundamentals are the building blocks of fun." She even feels this way about ballet, her beloved passion, leaving practice early when the class begins dancing freestyle. The day after the dish washing confrontation, Molly meets Ray at one of her ballet classes, apologizes for her behavior and asks for her job back. Molly gives Ray her pet pig Mu as a gift. Molly attempts to show Ray how to have fun, which at first causes them to fight. The two go to the amusement park Coney Island, only to find out that it is closed for the season.

That night, as they ride back home on the subway, Molly tells Ray about the night her parents died. As Ray goes to bed, the two get into a conversation about Molly, in which Ray accuses her of being scared of growing up. Molly begins to talk about an incident in her childhood shortly after her parents' death in which she ran away to Coney Island and sat down in the Spinning Teacup ride, spinning round and round over and over again. Molly begins crying and tells Ray that she had hoped they could go to Coney Island together. Ray holds Molly as she cries, and the two fall asleep in Ray's bed.

The next morning, Molly wakes up to find Ray gone. When she looks for her in the kitchen, she sees Neal there, and she finds out that he is sleeping with Roma in order to get a record deal. Later, Molly learns that Ray was in her father's room reading. She advises Ray to share her life with her father for his better recovery, telling her about a show she once saw about comatose people who recovered because their friends and relatives talked to them while they were still comatose. Ray does this, telling her comatose father all about Molly, ballet, and Mu. The next day, Molly arrives at Ray's house to find that Ray's father is gone from his room. She learns from the nurse that he had died that afternoon. Devastated, Molly rushes to Ray to offer her condolences. Ray is disturbingly emotionless, and calmly orders Molly to leave.

Later that night, Molly is called to Roma's office, where she is informed that she is fired. Molly begins to criticize Roma on her relationship with her daughter, saying she doesn't "...give her respect, you give her whatever she asks so that you don't have to deal with her." She then asks Roma if she knows certain things about Ray, such as what stage she is at in ballet, or how she likes to drink her tea. Molly tears up the payment Roma had given her, and angrily leaves her office.

Neal tries to get back together with Molly; since leaving her, he hasn't written a single song. But Molly refuses to be with him, as she now sees how selfish he is. She auctions her father's legendary guitar collection for financial support, and the whole collection is bought by a stranger on the phone. Days later, Molly gets a call from Roma, who tells her that Ray is missing and asks her for help. Molly searches desperately for Ray and eventually finds her in an amusement park sitting in the Teacup ride. The two ride the teacups for a bit, and afterward, as Ray vomits into a garbage can, Molly tries to comfort her. Ray at first reacts angrily and violently, but the two end up in a tearful embrace. Later, Molly attends Ray's father's funeral, where she reconciles with Ingrid, and sees that Roma is taking more of a part in Ray's life. Before Ray comes out to meet the rest of the guests at the funeral, she requests to speak to Molly alone.

After they talk, Molly tells Ray that they are going to be best friends. Ray says that grown-ups are never friends with kids, to which Molly responds, "I don't see any grown-ups around here." Molly applies for Fashion Institute of Technology and gets positive reactions from them. She attends Ray's ballet recital. In the recital, Ray wears the tutu Molly made for her, and Neal makes an appearance as the lead singer, singing "Molly Smiles", a song Molly's father wrote for Molly. As he sings, he plays on one of her father's guitars, and some of the ballerinas hold his other guitars as they dance, proving that Neal was the one who bought the entire collection. Near the end of the recital, Ray does a freestyle dance, much to Molly's amusement. The scene fades with a shot of Molly smiling in the audience, and the credits roll as a voice of Ray is heard: "Every story has an end. But in life, every ending is just a new beginning."