For the sake of his role in the movie, Farhan Akhtar had taken to solving the Rubik's cube. He became so passionate about it that he solved it wherever he went from parties to shoots to meetings. Since he is known to be a method actor and a perfectionist who believes in going through his paces beforehand, he began learning to unlock the puzzle much before the film hit the floors. He tagged the cube along with him everywhere and practiced it in his free time - in his car, at theaters or even in his office. And reportedly, very soon he became such an expert at it that he now throws challenges at others to beat him at it.
Since Deepika Padukone's character in the film is a smoker, she was required to smoke cigarettes on screen for the first time in her career. Deepika is strongly against smoking and due to this she almost declined doing the role altogether when she found out the character had to smoke, since she was worried that she herself may end up becoming addicted to cigarettes. However, the producer of the film, Ritesh Sidhwani, came to her rescue and ordered nicotine free "organic" cigarettes for her to smoke for the scenes in which she had to smoke. This relieved Deepika and everything was fine after that.
In an effort to create a more realistic performance for the movie by enriching his acting with the thoughts and emotions of his character, Farhan Akhtar had suddenly withdrawn into a shell, consciously trying to distance himself from the people around, during the course of the film's shooting. Since the part required him to be a lonely brooder Farhan (who is known to be utterly gregarious and accessible) switched off his phone and became almost inaccessible to the world outside. Friends found Farhan's behavior strange since usually he is so reachable and cheerful. For his role, Farhan said "It was the nature of the character I was playing. He's a guy lost in his world. So I was making an effort to isolate myself. Lately I've just been switching off from the world for the sake of my character. If you want to call it method acting, so be it."
Before the soundtrack album got released, an online copy was leaked onto the Internet. Farhan Akhtar confirmed this and requested not to download them illegally.
Deepika had to chop her long hair into a short lob for this role. The full video of the big chop is on YouTube.