The sources have revealed that Aamir will not have a single inch of clothes on his body for the scene. We all know that Aamir doesn't rely on such cheap publicity stunts nor does he like to have such obscene content in his movies.
So, it was director Raj Kumar Hirani who convinced Aamir to do the scene. Aamir initially didn't warm up to the idea, but after Hirani convinced him that it was important for the movie Aamir agreed to do it.
A source revealed, “Aamir Khan is essaying a role of alien in the movie who lands on earth by his choice. The nude scene is supposed to be the introductory scene of his character.”
Aamir could have asked for a body double for the scene, but Aamir being a perfectionist opted to do the scene on his own.