The film stars Karthi Sivakumar, Reema Sen and Andrea Jeremiah in lead roles. Parthiban also plays a pivotal role in the film. Aayirathil Oruvan tells a fantasy story that travels back and forth in time and is centered around four key characters. Reema Sen plays the role of a bio-scientist who invents a medicine with a potential to change the lives of people. Karthi plays a man who got transformed by the medicine. Shooting of the film began in July in 2007, but due to the extensive pre-production and post-production works the release of the film got delayed. The project started with an estimated Rs.15 crore budget but ended up with Rs.32 crores. Aayirathil Oruvan is produced by R. Ravindran. G V Prakash Kumar has scored the music for the film while lyrics are by Vairamuthu. Ramji has cranked the camera for the film while editing is by Kola Bhaskar. Aayirathil Oruvan is scheduled for release on January 14, 2010 coinciding with the festival of Pongal.

Om Prakash Makhija is a Junior Artiste in Bollywood, who is infatuated with actress Shantipriya, and hopes to marry her someday. His hopes come to reality when he rescues her from a fire and they go on a date. Shortly thereafter he finds out that she is married to a film producer, Mukesh Mehra, and is expecting his child. He then watches in horror as Mukesh, after luring her in an abandoned studio, sets it afire. Om attempts to rescue her in vain, and he eventually is killed. 30 years later, Om is reborn as the only son of yesteryear Bollywood actor, Rajesh Kapoor, and is himself an actor. His memories start to return when he meets with his widowed mother, Bela, from his previous birth. He also meets with Mukesh and together they decide to make a movie Om Shanti Om . Om then hires a look-alike of Shantipriya, and hopes to force a confession out of Mukesh - but things go awry and Om finds his life endangered once again.

Karan Kapoor and Rhea Prakash meet for the first time in a flight bound from Delhi to New York. They just cannot stand each other: Rhea is disgusted by Karan s flirtatious mannerisms and Karan is frustrated because of Rhea s overt seriousness. They have a massive fallout and part ways, vowing never to see each other s face again. Destiny brings them together again at Rhea s marriage ceremony three years later and the mars vs. venus war continues. Rhea gets married and leaves for USA. Four years later, Karan has become a successful cartoonist and travels to Paris to visit his father. Co-incidentally he meets Rhea again and learns that her husband is no more. Karan tries earnestly to bring happiness back in Rhea s life by promising her mother that he will find a suitable groom for Rhea but the duo never realizes that they are drawing closer to each other. Will love happen...