The story starts with an American visiting the Kalindi Temple at night. There he sees the priest of the temple in a horrific state – he had slit his body with a scythe and had written 'Om' on his body. The man, horrified by what he is seeing, flees from there. The story then shifts to a model in her early 20s, Nandita (Kangna Ranaut) who is in love with Yash, (Adhyayan Suman) a director and host of the reality show "Andhvishwas" a show dealing with various superstitions of ghosts and tantric voodoos. Yash gifts Nandita an apartment where they start living and they love each other, in the meantime Nandita gets pregnant.
Esha Malhotra (Esha Deol) is a bright, spirited girl who has just left college. She finds a note from a past student of her school that coincides with her own feelings of love. She calls into a radio station and requests a song, repeating the words left on the note. An anonymous man calls in soon after, stating that he is the one who had written the letter and he would like to meet her someday since they seem to have the same feelings about love and other aspects in life. The radio announcer sets up a date and time for their meeting at the radio station. The man arrives but finds only a letter waiting for him. The letter does not state her name or address, only a post box number to which she requests him to write to so that they can be friends. The correspondence begins. The man turns out to be photographer Rahul Sharma (Hrithik Roshan). They do not meet, exchange numbers or tell their names but continue to write each other. Fate brings the two together when Esha hires Rahul to be their photographer for a campaign, of course she didn't know it was him nor he did that it was her.
In 2008, Deepak Kumar (Saif Ali Khan) is at an interview for the teacher's post at an affluent school. The interviewers turn him down when they discover his low-caste roots. Deepak relates the incident to his mentor, Dr. Prabhakar Anand (Amitabh Bachchan). Dr Anand, the legendary principal of renowned STM college, offers Deepak an interim job as a teacher at STM. Deepak is comforted by his friend, Sushant (an upper-caste boy), and his girlfriend Poorbi (Deepika Padukone), who is Dr. Anand's daughter.
Roy Kapoor est le roi de l'arnaque, un maître incontesté du bluff. Peu de temps avant son mariage avec Simmi, il piège le producteur d'un film. Le jour de la noce, le producteur réapparaît, invité par la famille de Simmi. Ignorant tout des activités de Roy, Simmi ne peut contenir sa déception et fait annuler le mariage.
Roop Rathore (Shahrukh Khan) is a singer in Bombay just like his father (Anupam Kher), who is now sick and needs immediate medical care. One day, while he is singing at Ajay Narang's (Naseeruddin Shah) hotel, Ajay's sister Reshma (Ramya Krishnan) falls in love with Roop. Reshma is a spoiled girl and Ajay looks through all of her wishes. Unfortunately, Roop is in love with a doctor named Pooja (Pooja Bhatt). Meanwhile, Reshma is obsessed with Roop, and asks her brother to call him again to sing in their hotel. But when she sees that all the girls are flattered over Roop, she gets very angry, and asks him to sing only for her now onwards. But Roop would rather work for rival Patel (Shri Vallabh Vyas) than take this offer. Ajay's obsession with keeping his sister happy at all costs comes into play and Patel is brutally beaten by him until he agrees to throw Roop out of his hotel. Desperately in need of money for his father's operation, Roop has no option but to agree to Reshma. Roop breaks up with Pooja.
At the beginning, Izna, a porn star (Sunny Leone), is lying dead in the grass, but she says that she wants to ask forgiveness from somebody for her sins. The story flashes back six months.
Lallan Singh (Abhishek Bachchan) is a goon, originally from Bihar but settled in Kolkata, West Bengal because his brother Gopal Singh (Sonu Sood) has left him alone and he had no option of earning back home. He loves, marries and abuses his wife, Shashi Biswas (Rani Mukerji). Michael Mukherjee (Ajay Devgan) is an influential student leader who wants politicians like Prosenjit Bhattacharya (Om Puri) to keep away from college elections. Michael is in love with his neighbour Radhika (Esha Deol) who lives with her uncle and aunt. And then there is Arjun (Vivek Oberoi), carefree and spoiled son of an IAS officer. He wants to relocate to the U.S. for a better future. He falls in love with Mira (Kareena Kapoor), whom he just met. One day, Arjun and Mira get into a quarrel on the road and Mira gets into an auto. Arjun gets lift from Michael to catch up with Mira, who is going that way. Suddenly, Michael is hit by a bullet and he is saved by Arjun. After talking to Michael, Arjun changes his mind and wants to be a politician. Prosenjit is worried when he hears news of students standing in the election. He uses every possible way to get them out of Politics.Firstly he provides scholarship of a prestigious foreign university to Michael. When Michael refuses the bribe, he orders his goon Gopal Singh to take control. Gopal beats some students but faces very strong retaliation from Michael and his fellow students. After that Lallan Singh takes charge and kills Gopal. He kidnaps Arjun and other candidates. However, they manage to escape with the help of Lallan Singh's ally. Lallan follows Arjun and beats him up. While running, Arjun manages to call Michael for help. He comes to rescue Arjun at Howrah Bridge.
Maharashtra Police seizes a large quantity of arms from a house in the communal riot torn town of Chandangarh. The house belongs to Dr. Iqbal Ansari (Atul Kulkarni), a Muslim doctor. The police conclude that he is an agent for ISI, and is responsible for engineering the riots. Ansari is arrested as per Prevention of Terrorism Act, 2002 and is set to be presented before a special court in Mumbai. However, the convoy of police vehicles transporting Ansari from Chandangarh is ambushed by an unknown group. The police team somehow manages to secure him, but suffers heavy casualties. The unknown group, presumed to be terrorists, seems determined to free Ansari from the government's custody.
Subhash Nagre (Amitabh Bachchan), who is known by his followers as Sarkar, lives in Mumbai. The opening scenes show a rape victim's father (Veerendra Saxena) approaching Sarkar for justice (which the corrupt law and order system has failed to deliver) which Sarkar promptly establishes by having the rapist beaten up by his henchmen. His son, Vishnu (Kay Kay Menon), plays a sleazy producer who is more interested in the film actress Sapna (Nisha Kothari) than his wife Amrita (Rukhsar). Sarkar's other, more upright son, Shankar (Abhishek Bachchan), returns from the United States with his love Pooja (Katrina Kaif) after completing his education there. Pooja's doubts about Sarkar's image cause Shankar, who firmly believes in his father's righteousness, to break up with her later in the movie.
Anjaana Anjaani is the story of Kiara (Priyanka Chopra) and Akash (Ranbir Kapoor). Kiara is based in San Francisco, while Akash is a New York City boy. Akash has to clear a loan of $12 million, which he is unable to partly due to the stock market crash. Unable to find any means, suicide seems the only option. He decides to jump off the George Washington Bridge. This is when he meets Kiara, who is also bound to commit suicide because she caught her fiancé Kunal (Zayed Khan) cheating on her. They both try to put an end to their lives but are deterred by the coastguards. Still keen on ending their lives, Akash deliberately gets hit by a car and Kiara falls on the bridge and breaks her neck. This proves to be yet another failed attempt and they end up in the hospital together. Kiara takes Akash to her house as his house was seized by the bank.
Kabir (John Abraham), an unhappy, rather poor, alcoholic lawyer lives a playboy lifestyle in Pondicherry. Kabir's best friends, Siddharth (Vinay Pathak), a policeman and Vishal (Ranvir Shorey), his colleague, try to keep him away from trouble. He meets Sonia Khanna (Bipasha Basu), a beautiful wife of a travelling millionaire, Rohit Khanna (Gulshan Grover).
The film takes place in the impoverished village of Laholi where, following droughts, most of the villagers' possessions are mortgaged to the local Thakurani Karamkali (Sudha Chandran). One of the few entertainments the villagers can afford is the lottery, Malaamal Weekly (malaamal is Hindi for 'rich').
Suhaan (Salman Khan) and Piya (Preity Zinta) fell in love in college and eloped. However, he has to keep his marriage a secret in order to further his career as a movie star and, when his career hits a low, he returns home to find out that she has left him. She does not answer his calls or letters, and he soon receives divorce papers in the mail.