KOI...MIL GAYA is a story about a scientist that believes that there are aliens in the sky in a different planet. So he goes on his computer and does some research and gets a message from the aliens.So Sanjay (Rakesh Roshan) goes to meet the other scientist and they don't believe him so he goes back home with his pregnant wife (Rekha) and wile they are driving home something appears in the sky and Sanjay thinks that is a alien ship and he was looking at it. It got them a car crash Sanjay died but Rekha saves herself. When Rekha has a boy and during the car crash Rohit (HRITHIK ROSHAN) hurt his head and the doctors says that when he grows up his brain will still be like a 6 year old. So when Rohit grew up he had friends like 8 year olds and played with them. Everyone teased Rohit and Rohit all ways got upset and started to cry. Then all of a sudden he bumps in to some guys on a motor bike and they start acting cheeky with each other and they got tired of him and when they always see him they would bully him. Rahul the gang leader would bully him is well.
Then all of a sudden Nisha (Priety Zinta) comes in and she is a best friend of Rahul. Nisha and Rohit get to a bad start at first but then they become best friends. Nisha and Rohit go on there father's computer and they start thinking its a normal computer so they star playing with it but one thing they don't know is that computer is to keep in touch with the aliens. All of a sudden a ship shows up from the sky and its the aliens ship. Everyone is very scared and the next day they forget about it but the police didn't forget and wants to know what happened about the ship. The police find out that it was an alien that was here because all the aliens went back to the ship but looking at the foot prints on the ground of one alien didn't go back so the police are looking for the alien. Nish and Rohit go to the woods just to see if its true and all of a sudden a alien jumps out from the tree and then they both realised that the alien is in trouble so they took the alien to Rohit's house and hide him there with out anyone finding out and his mum.
Rohit's friends find out about the alien but they keep it a secret. Rohit becomes friend with the alien and they treat him well. Then all of a sudden Rohit wants to play basket ball and Rahul and his gang tease him and then Rohit goes home crying in front of the alien and next morning Rohit can see with out his classes and is also cleaver at every think and also can play basket ball and dancing then he becomes cool and fit. He starts falling in love with Nisha and also Nisha starts falling in love with Rohit. The police are still looking for the alien but all of a sudden Rohit's mum sees the alien she was about to call the police but all of a sudden she gets a call from the teachers saying that Rohit is cleaver at school and that's all because of the alien and they also named the alien jadoo so Rohit's mum starts to like him and wants to help him.
All of a sudden the police find out that Rohit has got jadoo so they try to get him so they do and Rohit gets him back and takes him back to the ship by going on the same computer and gets the aliens ship but before he went jadoo said if he goes back then he will take all the power away from Rohit. He will be the same as before like a 6 year old but they didn't care they just wanted to save jadoo so he goes back to his world and never comes back again. Rohit is himself again and he becomes famous everyone loves him for what he did for the alien. Rohit and Nisha are walking on the roads and talking then all of a sudden Rahul sees him and starts to tease him and says kick the ball see how high you can kick it so he gets so angry and kicks the ball so high and then all of a sudden he can see without his classes so that means that jadoo gave all his powers back to Rohit and know he is clever again and is fit and fine.
So that's the story of KOI...MIL GAYA if you haven't seen this film go out and watch this film. This was the best and Hrithik Roshan got an award for this film.