The first film in India to be given a UA certificate on account of violence and not sexual content.
The mobile phone number imprinted on Aamir Khan's body shown in the movie turned out to be a real phone number used by a woman in Bangalore. After the movie was released she got lots of calls and texts. Even though the distributors of the film wanted to help her, the posters of the movie showing Aamir's toned body with tattooed number were marketed widely before the movie released. (See also Bruce tout-puissant (2003).)
It was Aamir Khan's strong decision Asin remained in the movie, the producers were not interested in casting South Indian actresses opposite Aamir. Their choice to play Kalpana was Priyanka Chopra Jonas. Later producers agreed to go with Aamir's choice.
Anil Kapoor revealed in an interview that Christopher Nolan was upset that they didn't give him any credit or money as the film is inspired by his movie Memento (2000) when he met him in Hollywood. However Nolan and the Ghajini crew talked over and everything got sorted out later.
According to Aamir, the things excited about Ghajini (2005) was the action, the story, the screenplay and the love story in the film. But he was a bit hesitant whether to do the film or not. It was original actor Suriya convinced him to do the movie telling that he is the only one who can do justice to the character. And after meeting with director A.R. Murugadoss, Aamir finally set to start the Hindi version of Ghajini.