The film is set in a town called Vasco in Goa, named after Alberto Vasco, a Portuguese noble who owned most of the town during the colonial era. There are two rival gangs in Vasco, called the Bichhoos (Scorpions in Hindi), who are Hindus, and the Eagles, who are Christians.
A street-toughened orphan by the name of Munna (Aamir Khan) is befriended by some kind folks, whose effervescent daughter Mili (Urmila Matondkar) soon grows to be his best buddy. Both gravitate toward the Mumbai movie industry. While Mili finds occupation as a movie extra, Munna earns his livelihood selling movie tickets in the black market.
Dev Narayan (Alok Nath) lives with his widowed daughter Laxmi (Aruna Irani) and her children Radha and Prashant. Dev also looks after two orphaned children, Gopal and Nita. Laxmi believes that Dev is taking more care of Gopal and Nita, so she leaves the house with her children. Laxmi soon spots an orphaned boy on the streets and takes him in. Radha forms a sisterly bond with him and names him Suraj. Suraj has a particular passion for singing.
The story revolves around Shanaya (Bipasha Basu), an actress at the height of her success. She gets offered the best roles and wins all the awards she is nominated for. In addition, she also has a passionate affair with a handsome director named Aditya (Emraan Hashmi). This all ends when a younger actress, Sanjana (Esha Gupta) makes her film debut. In place of Shanaya, Sanjana comes into spotlight and begins to snatch away her awards. Suddenly, Shanaya seems forgotten and everybody only wants to work with Sanjana. Soon enough, Shanaya sees her career fading away and her envy slowly becomes craziness. She begins to turn to black magic and makes it her goal in life to destroy Sanjana's career and make her the pain of loss.
Kishen (Anil Kapoor) has a suspicious-minded wife, Kaajal (Lara Dutta), who thinks he is always having an affair with another woman, even though he is extremely faithful to her and wouldn't dream of betraying her in any way. Prem (Salman Khan) has the opposite situation. He is married to Pooja (Esha Deol), who seems to be very trusting, even though he has been having several affairs with numerous gorgeous women. There is also Kishen's friend Shekhar (Fardeen Khan), who accidentally falls in love with Sanjana (Celina Jaitley) and marries her. Then Bobby (Bipasha Basu), a call girl, enters the story. When Kishen takes pictures of Prem and his girlfriend, and threatens to send them to his wife, Prem hires Bobby to seduce Kishen. The plan is that Kishen will fall in love with her, and Prem wants to see if Kishen can hide the relationship. Then the lies start happening, as Kaajal thinks Bobby is Shekhar's wife, and Sanjana thinks Bobby is Kishen's wife. It becomes a bundle of confusion and comedy when all the various people and couples start meeting.
The retired Dean of St. Teresa College, Yogindra Vashist (Rishi Kapoor), lies gravely ill in hospital. As some of his former students gather at his deathbed, Kaizaad "Sudo" Sodabottleopenerwala (Kayoze Irani), Tanya Israni (Sana Saeed), Jeet Khurana (Sahil Anand) and Shruti Pathak reminisce about their student years in St. Teresa College ten years before, and the events that led up to the present day.
In the early 1900s, Kaushalya (Smita Jaykar) hears that her younger son, Devdas (Shah Rukh Khan), is to return home after he had left 10 years ago for law school in England. Kaushalya tells her neighbor Sumitra (Kirron Kher), who is overjoyed. Sumitra's daughter, "Paro" Parvati Chakraborty (Aishwarya Rai) and Devdas have shared a deep friendship since childhood. When Devdas went to England, Paro had lit an oil lamp to prompt his early return and never allows it to extinguish.
Naina Catherine Kapur (Preity Zinta) is a bespectacled 23-year-old Punjabi MBA student who is quite pessimistic and cynical towards her life and relationships. The movie opens up to Naina visiting Brooklyn Bridge Park in New York City. She relates how whenever she misses her father, she comes to the park. Upon returning home, we see Jenny (Jaya Bachchan), Naina's widowed mother who is on the phone discussing a loan extension for their centrally situated restaurant which isn't doing so well. Upon Naina's father's passing, all the house's responsibilities have fallen on her. Naina begins looking through the mail to find another private and confidential letter addressed to her mother, among many others she periodically receives. She also finds a letter from a Punjabi matrimonial service, Kunwari Kudi (meaning: Single Girl) that her grandmother and her aunts have enlisted in hopes of marrying off Naina to a Sikh sardar man. Naina's grandmother Lajjo (Sushma Seth), and Naina's aunts Kammo (Shoma Anand) and Vimmo (Kamini Khanna) are religious aspiring musicians who often perform for their neighbor, Chadda (Dara Singh) and to the horror and inconvenience of many of their other neighbors. There are also Naina's younger siblings in the home, including Shiv (Athit Naik), Naina's disabled biological brother and Gia (Jhanak Shukla), Naina's adoptive sister. There is much tension in the Kapur household as Lajjo is resentful towards Gia and Jenny as she believes Jenny's decision to adopt Gia is what led to her husband's suicide and the failing financial condition of their family, thus causing her to be affectionate with Naina and Shiv, while being cold to Gia. She thinks that Gia is the main problem in the house. She believes that the problems in the house started after Gia is adopted. There is also much religious tension in the house as Jenny practices Christianity while Lajjo practices Sikhism.
Amar Kant Varma (Shahrukh Khan) is a Program executive for All India Radio. He is dispatched from New Delhi to cover festivities in Northeast India. On his way there, during a rainy night, Amar stops at Haflong train station to catch Baraks Valley express, as the train runs late, Amar meets a mysterious woman by herself who asks him for a cup of tea. When he returns with the tea, he watches her board the next train with three male passengers. Later, Amar spots the same woman in Silchar. He attempts to talk to her but she says she cannot recall meeting him before. As part of his news reporting assignment, for the occasion of fifty years of Indian Independence, Amar interviews many citizens of Barak Valley, and an extremist leader, who claim that the reason behind human rights violations, and poverty in the region is due to Indian Government, and that the Liberationists do not wish to enter into any dialogue with the government, and further justify their resistance in Utthar Purv.
The film is about Rahul (Shahrukh Khan), a middle class man, reveling in a job with extra earnings made by helping his boss deal with his multiple extra-marital affairs. His boss, Siddharth (Aditya Pancholi), is a lustful person who has deviously trapped a rich woman (Kashmira Shah) and married her to own her property.
Simran (Sonam Kapoor) loves Bollywood romances so much so that her life has begun to resemble one. With her awesome job and a "Mr. Perfect" fiancé, Raj (Sameer Dattani), she lives a dreamy life. But then comes Jay (Imran Khan), who brings a fresh joy into her life. Jay is an assistant to a director who is famous for his love story films; however, Jay hates love stories. He is a disbeliver of love. He first hates Simran for her obsession with romance, and Simran also has a bad impression of him, but soon after, the two become friends.
Aditya (Vivek Oberoi) and his friends are searching for Aditya's wife Suhani (Rani Mukherji). She has been missing for hours, a few days after having a fight with Aditya, due to their failing marriage. But Aditya now realizes that he loves her more than anything and is devastated that he can't find her.
The story starts in the city of Mumbai where a motorbike gang starts breaking into banks and other public places and vanishing on Western Express Highway.
Kajal (Divya Bharti) falls in love and marries a famous singer named Ravi (Rishi Kapoor). They live happily until tragedy strikes: Ravi's greedy uncle Pratap (Amrish Puri) and cousin Narender (Mohnish Behl), are determined to lay their hands on Ravi's wealth. Narender first tries to rape Kajal but fails when he is caught. Pratap then hires hoodlums to murder Ravi, who is thrown off a cliff along with Pratap's son, Narender.
Raj (Salman Khan) is a singer trying to make his way in the big city of Mumbai. He rescues a young woman who has fallen in front of a train and stays with her when she is rushed to a hospital. Pooja Oberoi (Rani Mukerji), the daughter of a wealthy family, survives but falls into a coma. Her family rushes to the hospital and, finding Raj there, assumes that he is Pooja's husband, Romi, with whom she had eloped and whom they had never met. Pooja cannot correct them; Raj, who can, prefers not to out of kindness.