In 2002 Marni (Kristen Bell) is an acne-riddled high school sophomore at Ridgefield High School, with glasses and braces, making a video about how much she hates high school, and reveals how she is tormented and bullied by other children, specifically J-J (Odette Yustman), who made Marni's high school life miserable. She adds that her protective older brother, Will (James Wolk), was very popular as a handsome basketball player. However, at a very important basketball game, J-J pushes the mascot (Marni), who runs into Will, resulting in a loss of the game.
The film's central story concerns a father, Lalit Verma (Naseeruddin Shah), who is trying to organize an enormous, chaotic, and expensive wedding for his daughter, Aditi (Vasundhara Das), for whom he has arranged a marriage with a man, Hemant Rai (Parvin Dabas), she has known for only a few weeks. As so often happens in the Punjabi culture, such a wedding means that, for one of the few times in each generation, the extended family comes together from all corners of the globe, including India, Australia, Oman, and the United States, bringing its emotional baggage along.
Identical twins Susan Evers and Sharon McKendrick meet at summer camp, unaware that they are sisters. Their identical appearance initially creates rivalry, and they continuously pull pranks on each other, which ultimately leads to the camp dance being crashed by their mischief. As punishment, they must live together in an isolated cabin (and eat together at an "isolation table") for the remainder of their time at summer camp. After both admit they come from broken homes, they soon realize they are twin sisters and that their parents, Mitch and Maggie, divorced shortly after their birth, with each parent having custody of one of them. The twins, each eager to meet the parent she never knew, switch places. They drill each other on the other's behavior and lives, and Susan cuts Sharon's hair into the same style as hers. While Susan is in Boston masquerading as Sharon, Sharon goes to California pretending to be Susan.
Ambitious high-flyer Nat (Rose Byrne) and struggling writer Josh (Rafe Spall) fall in love at first sight at a party. After 6 months together they decide to marry. The film highlights their struggles during their first year of marriage, switching back and forth from flashbacks of the year's action to a marriage-guidance counsellor's office. Their wedding goes as planned despite many friends' comments that the marriage will not last, an embarrassing best man's speech and a coughing priest.
Prem (Salman Khan) lost his parents at an early age. He lives with his elder brother Rajesh (Mohnish Bahl) and uncle Kailashnath (Alok Nath). Rajesh manages the family business and his family is on the look-out for a suitable bride for him. Professor Siddharth Chaudhary (Anupam Kher) and Mrs. Chaudhary (Reema Lagoo) have two daughters, Pooja (Renuka Shahane) and Nisha (Madhuri Dixit). The Chaudhary couple and Kailashnath are old friends who meet again after several years. They arrange a marriage between Rajesh and Pooja. From their first meeting, Nisha and Prem start bickering lightheartedly with each other, and the fun and mischief continues throughout Pooja and Rajesh's wedding.
Steve Tobias (Michael Douglas) is an undercover agent of the CIA whose son, Mark (Ryan Reynolds), is getting married to Melissa Peyser (Lindsay Sloane). Her father is mild-mannered foot doctor, Jerry Peyser (Albert Brooks). When the two families meet for dinner, Peyser stumbles on to Steve Tobias' secret operation as Tobias tries to set up a deal to sell a Russian submarine, the Olga, to an arms smuggler in France as a bait. As Peyser's incidental involvement increases, he is suspected by the FBI of being part of a seemingly malicious deal. Dragged kicking and screaming, Peyser decides he does not want to be involved in the deal or with Tobias' family. The two fathers-in-law end up dodging bullets, jumping off buildings, and stealing jets together as they attempt to avoid capture by the FBI.
Max, un organisateur de mariage expérimenté, doit gérer le mariage de Pierre et Héléna dans un château de prestige. Il doit faire appel à une équipe de serveurs, trouver des cuisiniers, un photographe, un orchestre et un animateur tout en gérant les demandes et problèmes de chacun, mais aussi les siens.
High school sophomore Samantha "Sam" Baker (Molly Ringwald) struggles to get through the day on her 16th birthday, which her entire family has forgotten about because her older sister, Ginny, is getting married the next day. She is also plagued by infatuation with a popular and attractive senior, Jake Ryan (Michael Schoeffling). At school she fares no better when she finds out that a completed "sex quiz," which she tried to surreptitiously slip to her friend, never reached her friend and, unbeknownst to either of them, was picked up by Jake. Sam panics because the quiz contains sensitive information, such as she is a virgin and is saving herself for Jake.
Patrick Sullivan (Jeffrey Dean Morgan) is looking forward to a life with, Sophia (Justina Machado), until she calls into the show by famed love expert and radio host Dr. Emma Lloyd (Uma Thurman). Emma questions Sophia’s concept of romantic love and advises her to break their engagement, which she swiftly does.
Don and Ellie Griffin were a New England couple married for twenty years before they divorced. They have three children from their marriage – Lyla, Jared, and adopted son Alejandro, who was from Colombia.
Kym (Anne Hathaway) is released from drug rehab for a few days so she can go home to attend the wedding of her sister Rachel (Rosemarie DeWitt). At home, the atmosphere is strained between Kym and her family members as they struggle to reconcile themselves with her past and present. Kym's father (Bill Irwin) shows intense concern for her well-being and whereabouts, which Kym interprets as mistrust. She also resents her sister's choice of her best friend Emma (Anisa George), rather than Kym, to be her maid of honor. Rachel, for her part, resents the attention her sister's drug addiction is drawing away from her wedding, a resentment that comes to a head at the rehearsal dinner, where Kym, amid toasts from friends and family, takes the microphone to offer an apology for her past actions, as part of her twelve-step program.
Hairdresser Ida, who has recently ended a successful breast cancer treatment, returns home to find her husband Leif cheating on her. At the same time, her daughter is getting married in an Italian villa with a lemon orchard in a few days, and on the way there she runs into Philip, the groom's father. At the wedding, which is eventually called off when the putative bride and groom find that they are not, after all, right for one another, Ida and Philip develop an attraction. On their return to Denmark, Philip decides to reduce his workload and move permanently to Italy. He finds Ida at the hairdressing salon where she works, only to be rebuffed as she has returned to Leif. But Ida then has second thoughts and goes to Italy to be with Philip.
Molly de Mora (Paula Marshall) invites her divorced parents (Bette Midler and Dennis Farina) to her wedding reception, where they see each other for the first time in 14 years. A shouting match between the two ensues. Following this, their spark is rekindled during the wedding reception. Over the next few days they fall in love again and run off together, thereby upsetting the newlyweds' honeymoon and their respective (current) spouses. If the scandal was made public it would be more controversial than usual, since the bride's husband hopes to stand for election to Congress. After searching for her parents and getting to know Joey Donna (Danny Nucci), her mother's number one paparazzi nicknamed "The Cockroach", whom she hires to help her find them, Molly decides that her parents deserve a chance to be together and gives them her honeymoon to Hawaii. When Keith objects to her decision, it is revealed that he slept with her stepmother. Knowing now that her marriage was a mistake, Molly runs off with Joey as her parents run off to Hawaii.
The film begins with an introductory sequence involving the main characters and images from space and introducing many of the film's visual leitmotifs. These are motifs of virtually still images revealing the key elements of the film: Justine the bride in deep melancholy with birds falling behind her; of a lawn with trees and sundial with two different shadows; Pieter Breughel's Hunters in the Snow (often used as interpretation of an idealised nostalgia) burning; the non existent 19th hole (limbo) and the Black Horse collapsing catastrophically in slow motion (Id, ego and super-ego battle); Justine as a bride being swept along by a river; and her being held back by her wedding dress; and finally Justine and her nephew building their magic cave before the Earth crashes into Melancholia becoming one.