Plot

A brilliant scientist creates a humanoid robot to protect mankind, but things go awry when human emotions are programmed and inner turmoil causes the robot to switch sides.

Dr. Vasi (Rajnikanth) invents a super-powered robot, Chitti, in his own image. The scientific body, AIRD, that must approve the robot, declines it based on its not having emotions and the ability to make rational judgment. A sudden flash of lightning evokes emotions in the robot, and Chitti is seemingly ready for integration into the human world. Then, Chitti falls in love with Dr. Vasi's fiancée Sana (Aishwarya Rai) and turns on his creator.—Joyojeet Pal

Chennai-based Dr. K. Vaseegaran spends day and night in constructing a human-android, and after many trials and errors does succeed in creating one in his own image. His girlfriend, Sana, decides to name him Chitti, and is very impressed by the way he not only rescues her from goons on a train, but also a woman from a fiery building; delivers a baby in the maternal ward of a hospital; and instructs mosquito's to keep away from her. Impressed by these turn of events, Vaseegaran decides to make Chitti more human by letting him feel emotions - this results in the latter not only rebelling but also getting obsessed with Sana and embarrassing the couple on the occasion of their formal engagement. Furious at these turn of events, Vaseegaran terminates Chitti and has it disposed off. But Dr. Bohra, who expects to net millions by such an android, reconstructs Chitti with a different chip - with results that will enable it to assist him to re-produce more such androids - as well as give the now malevolent, virtually indestructible and unstoppable Chitti the freedom to pursue Sana and re-populate Earth with a new species - Robo-Sapiens!!—rAjOo (gunwanti@hotmail.com)

Vaseegaran has spent years on making a human Robot staying away from his family and fiance Sana.When he completes the project he gets him home where his mother names him Chitti.Vaseegaran introduces Sana to Chitti and he helps her in many ways.Proffesor Bohra mentor of Vaseegaran is working on similar project but is unsuccessful.During evaluation he fails Chitti claiming it to just be a machine without any feelings.Vaseegaran then starts to work on Chitti in process of developing feelings towards women.After Chitti starts developing feelings towards human he starts to fall in love with Sana.Vaseegaran sees his project failing and destroys Chitti.Bohra takes advantage of this and re creates Chitti but to cause destruction.—alex.mjacko@gmail.com

After a decade of research, the scientist Vaseegaran (Rajinikanth) creates a sophisticated android robot with the help of his assistants, Siva (Santhanam) and Ravi (Karunas), to commission it into the Indian Army. Vaseegaran named the robot Chitti. Chitti is extremely powerful and yet follows the laws of robotics. Chitti has a speed of 1 Terahertz and a memory of 1 Zettabyte.

During the development of Chitti, which last several months, Vaseegaran completely ignores his girlfriend, Sana. Chitti is designed by Vaseegaran using his own body as a reference cast, and Vaseegaran input his mannerisms and body movements into Chitti. Chitti is loaded with knowledge of music, sports, language and all other topics in his memory banks. Chitti's eyes have an inbuilt projector, and he is fireproof.

Vaseegaran had worked on the project for over 10 years. With artificial skin, Chitti looks an exact copy of Vaseegaran. To test Chitti, Vaseegaran decides to take Chitti into the outside world and observe Chitti's interactions with normal humans. Vaseegaran lives with his parents, father (Delhi Kumar) and mother (Revathi Sankaran).

Once his project is complete, Vaseegaran reconnects with Sana and apologizes to her for his absence. The acclimatization project has its hiccups when a policeman asks for a "cut" from Chitti when he was caught parking in a no-parking zone, and without driving license. Chitti proceeds to put a cut on the policeman's hand with a knife.

Vaseegaran introduces Chitti (Rajinikanth), at a robotics conference in Chennai. Vaseegaran's mentor, Professor Bohra (Danny Denzongpa), is secretly engaged in a project to create similar android robots for a terrorist organization but has so far been unsuccessful. Threatened with death if he fails to meet the deadline, Bohra seeks the details of Chitti's Neural Schema, intending to program his robots correctly. Vaseegaran refuses to share the Neural Schema of Chitti saying that it can be misused till the time it is properly patented and protected.

Chitti helps Sana (Aishwarya Rai), Vaseegaran's medical student girlfriend, to study for her examination. Sana runs Happy Homes, an organization for the welfare of Army widows. Some thugs were playing loud music just outside her home. When Sana confronts the thugs, Chitti remote controls the music system and breaks it by turning the volume to its maximum possible. Next, religious goons play loud music for an all night Jagrata, and Chitti destroys their music system. The goons attack Chitti and he defeats them easily. Due to these interruptions Sana had no time to study. Chitti reads the entire syllabus in seconds. He then sits outside the exam center and relays the answers to Sana via Bluetooth. But Chitti is caught midway. He gets into the ventilation ducts and gets above Sana's seat and projects the answers into her answer sheet.

Both groups of thugs from before corner Sana on the local train and Sana orders Chitti to beat them, but this time Chitti is damaged and runs low on battery power. The thugs throw Chitti out of the train and prepare to sexually assault Sana. Chitti charges himself on a track-side electricity supply box and re-enters the train to defeat the goons and save Sana.

Vaseegaran prepares Chitti for an evaluation by the Artificial Intelligence Research and Development (AIRD) Institute, which is headed by Bohra. During the evaluation, Chitti attempts to stab Vaseegaran at Bohra's command, which convinces the evaluation committee that the robot is a liability and cannot be used for military purposes. Vaseegaran's effort to prove Bohra wrong fails when he deploys Chitti to rescue people from a burning building. The robot saves most of them, including a girl named Selvi who was bathing at the time, but she is ashamed of being seen naked on camera and flees, only to be hit and killed by a truck. Vaseegaran asks for one month to modify Chitti's Neural Schema to enable it to understand human behavior and emotions, to which Bohra agrees. While nearing the deadline, Vaseegaran insults Chitti, who becomes angry with Vaseegaran, demonstrating to him that it can manifest emotions. Vaseegaran is delighted and hugs Chitti.

Chitti uses Sana's textbooks to successfully help Sana's sister Latha (Devadarshini) give birth to a child. Bohra congratulates Vaseegaran on the achievement and allows Chitti to pass the AIRD evaluation. Chitti develops romantic feelings for Sana after she congratulates Chitti by kissing it. Later, at Sana's birthday party, Chitti seduces her while dancing and is confronted by Vaseegaran and Sana, to whom it confesses its love towards her. Vaseegaran reprimands Chitti, while Sana explains that they can only be friends.

Chitti is saddened by her rejection, until Bohra convinces it to fight for its love for Sana, at Vaseegaran's expense. Chitti deliberately fails an evaluation conducted by the Indian Army, resulting in Vaseegaran chopping Chitti into pieces, which Siva and Ravi dump into a landfill site.

Bohra visits the site to retrieve Chitti, which has now reassembled itself, albeit in a damaged state. Bohra embeds a red chip inside Chitti while reconstructing it, converting it into version 2.0, which is more aggressive and unsympathetic. When Siva and Ravi ask why he is doing this, Bohra reveals his true intentions that he is doing this to earn money through his business and defame Vaseegaran, scaring them. Chitti then gatecrashes Vaseegaran and Sana's wedding, kidnaps Sana, creates replicas of itself and kills Bohra. Using its robot army, Chitti occupies AIRD and causes mayhem in the city.

After informing Sana that it has acquired the human ability to reproduce, Chitti wishes to marry her so that a machine and a human being can give birth to a programmed child, but Sana refuses. It eventually finds Vaseegaran, who entered AIRD to stop it, and nearly kills him before the police appear. The ensuing battle between Chitti's robot army and the police personnel leads to a lot of property destruction and many casualties. Vaseegaran eventually captures Chitti using a magnetic wall and accesses its internal control panel, whereby he instructs all the other robots to self-destruct. He then removes Chitti's red chip, calming it.

In a court hearing, Vaseegaran is sentenced to death for the casualties and damages caused by the robot army, but Chitti explains that it was Bohra who caused its deviant behavior and shows the court video footage of Bohra installing the red chip. The court releases Vaseegaran, while ordering that Chitti be dismantled. Left with no choice, Vaseegaran asks Chitti to dismantle itself. While saying goodbye, Chitti apologizes to Vaseegaran and Sana, who forgive it, before dismantling itself.

Fast forward to 2030. Chitti is now a museum exhibit. A curious school student on excursion asks her guide why it was dismantled, to which Chitti responds, "I Started Thinking"