The film opens on a stormy Alabama beach with two children, Melanie Smooter and Jake Perry, chasing each other. Jake has brought Melanie out to show her the glass sculptures that result when sand is struck by lightning. They discuss their future together, with Jake asserting they will be married one day. They kiss and are almost struck by lightning.
In the year 1900, a depressed British writer named Christian (Ewan McGregor) begins writing on his typewriter ("Nature Boy"). One year earlier, Christian moved to the Montmartre district of Paris to become a writer among members of the area's Bohemian movement. He soon encounters, living directly upstairs from him, a loose troupe of performers led by Henri de Toulouse-Lautrec (John Leguizamo). Toulouse-Lautrec and the others ask for Christian's help, and his writing skills allow them to finish their proposed show, "Spectacular Spectacular", that they wish to sell to the owner of the Moulin Rouge, Harold Zidler (Jim Broadbent). The group arrives at the Moulin Rouge as Zidler and his "Diamond Dog Dancers" perform for the audience ("Lady Marmalade/Zidler's Rap (Can Can)/Smells Like Teen Spirit"). Toulouse arranges for Christian to see Satine (Nicole Kidman), the star courtesan, in her private quarters to present the work, unaware that Zidler is promising Satine to the wealthy and unscrupulous Duke of Monroth (Richard Roxburgh), a potential investor in the cabaret ("Sparkling Diamonds" medley).
Nine people in Baltimore deal with their respective romantic problems, usually thwarted by the differing ideals and desires of their chosen partner. At the center of this is Gigi Phillips (Ginnifer Goodwin), a young woman who repeatedly misinterprets the behavior of her romantic partners.
Reuben Feffer (Ben Stiller), an insurance actuary, is celebrating his honeymoon with newlywed wife, Lisa Kramer (Debra Messing), on the island of St. Barts but catches her having sex with Claude (Hank Azaria), a French scuba instructor. Returning home to New York alone, he attempts to piece his life back together. Reuben goes to an art gallery with his friend, Sandy Lyle (Philip Seymour Hoffman), where he runs into former junior high school classmate Polly Prince (Jennifer Aniston).
Andie Anderson (Kate Hudson) is a writer who works for a magazine called Composure as the "How to..." girl. She is bored and wishes she could write more about important things, such as politics, economics, religion, poverty; stuff she actually cares about. She soon finds herself writing an article called "How to Lose a Guy in 10 Days". The idea comes about when Andie's friend, Michelle (Kathryn Hahn), experiences a minor breakdown after yet another break-up. Using her friend as inspiration, Andie reveals how she will actually start dating a guy and drive him away but "only using the classic mistakes women make".
Andy Stitzer (Steve Carell) is a 40-year-old virgin who is involuntarily celibate. He lives alone, collects action figures, plays video games, and his social life seems to consist of watching Survivor with his elderly neighbors. He works in the stockroom at an electronics store called SmartTech. When a friend drops out of a poker game, Andy's co-workers David (Paul Rudd), Cal (Seth Rogen), and Jay (Romany Malco) reluctantly invite Andy to join them. At the game (which he wins, due to playing online poker constantly), when conversation turns to past sexual exploits, Andy desperately makes up a story, but when he compares the feel of a woman's breast to a "bag of sand", he is forced to admit his virginity.
Michael Dorsey (Dustin Hoffman) is a respected but perfectionist actor. Nobody in New York wants to hire him anymore because he is difficult to work with. According to his long-suffering agent George Fields (Sydney Pollack), Michael's attention to detail and difficult reputation led a commercial he worked on to run significantly over-schedule, because the idea of a tomato sitting down was "illogical" to him. After many months without a job, Michael hears of an opening on the soap opera Southwest General from his friend and acting student Sandy Lester (Teri Garr), who tries out for the role of a hospital administrator Emily Kimberly but does not get it. In desperation, and as a result of his agent telling him that "no one will hire you", he dresses as a woman, auditions as "Dorothy Michaels" and wins the part. Michael takes the job as a way to raise $8,000 to produce a play, written by his roommate Jeff Slater (Bill Murray) and to star Sandy, titled Return to Love Canal. Michael plays his character as a feisty, feminist administrator, which surprises the other actors and crew who expected Emily to be (as written) another swooning female in the plot. His character quickly becomes a television sensation.
Amélie Poulain was raised by eccentric parents who — erroneously believing that she had a heart defect — prevented her from meeting other children. She was home schooled by her mother. She developed an active imagination and fantasy life to cope with her loneliness. After her mother is killed in a freak accident, her father's withdrawal from society worsens. Amélie eventually decides to leave home and becomes a waitress at Café des 2 Moulins in Montmartre, which is staffed and frequented by a collection of eccentrics. Spurning romantic relationships after a few disappointing efforts, she finds contentment in simple pleasures and letting her imagination roam free.
Eight years have gone by since Scott Calvin (Tim Allen) first took up the Santa Claus suit, and became subject to The Santa Clause. Now Santa is at the top of his game at the North Pole and could not be happier, at least until Bernard (David Krumholtz) and Curtis (Spencer Breslin), the Keeper of the Handbook of Christmas break the news that there is another clause - the "Mrs. Clause".
Dave (Vince Vaughn), a dealer for Guitar Hero, and Ronnie (Malin Åkerman), a stay-at-home mom, are a typical couple with two young children. They experience various stresses including redecorating their house and raising their kids. Joey (Jon Favreau) and Lucy (Kristin Davis) are high school sweethearts with a smart but naive teenage daughter named Lacey. Their relationship is on the rocks. Jason (Jason Bateman) and Cynthia (Kristen Bell) are a neurotic couple who've experienced multiple failed attempts to conceive, and Shane (Faizon Love), who has recently separated from his wife, has a much younger twenty-year-old girlfriend, Trudy (Kali Hawk).
Preston Blake, hoping to be a disc jockey as a young man, slowly worked his way up and founded Blake Media, a major corporation running hundreds of television and radio stations with 50,000 employees. After 82-year-old Blake freezes to death on the summit of Mount Everest with a triumphant smile on his face, a search for his heir begins.
John Clark (Richard Gere) is a lawyer with a charming wife (Beverly, played by Susan Sarandon) and loving family, who nevertheless feels that something is missing as he makes his way every day through the city. Each evening on his commute home through Chicago, John sees a beautiful woman staring with a lost expression through the window of a dance studio. Haunted by her gaze, John impulsively jumps off the train one night, and signs up for ballroom dancing lessons, hoping to meet her.
A zookeeper named Griffin Keyes (Kevin James) sets up a plan to propose to the love of his life Stephanie (Leslie Bibb), but she rejects him and claims that his career as a zookeeper is what is keeping her away, therefore breaking Griffin's heart.
15-year-old Mia Thermopolis lives with her artist mother Helen and her cat Fat Louie in a renovated San Francisco firehouse. Mia is a somewhat gawky, unpopular girl who is terrified of public speaking, even in class, and is seemingly invisible to her crush, Josh Bryant, and mocked by his cheerleader girlfriend, Lana Thomas. Mia’s only real friends are the equally unpopular Lilly Moscovitz and Lilly's brother Michael, who secretly has a crush on Mia.
Robin Monroe, a New York journalist working for Dazzle, a fashion magazine, is invited by her boyfriend Frank to spend a week holidaying with him on the island paradise of Makatea, in the South Pacific. The final leg of their journey to Makatea is in a small dilapidated aircraft, piloted by middle-aged American Quinn Norris. They are accompanied by Quinn's girlfriend and co-pilot Angelica.