The most Herculean task about the latest release PAA was transforming a 67-year old Amitabh Bachchan into 13-year old child Auro, suffering from a rare disorder called progeria. So come let's take a short run-through over how Amitabh became Auro.
Now you can see what's hidden
The prosthetic makeup, as we know, has been done by Hollywood's Christien Tinsley (THE PASSION OF THE CHRIST, CATWOMAN) and Dominie Till (THE LORD OF THE RINGS TRILOGY). 
According to the reports Bachchan's make-up cost 10 per cent of the total budget. 
It is learnt that it used to take four to five hours daily for Amitabh Bachchan's makeup to be done for his film PAA.
Not only this, if it used to take four hours to put on the make-up then two hours to remove it. 
There are eight different layers of clay which has been put in his make up in the film.
While applying the make up he cannot eat, drink and talk for four hours.
Most of the performance comes out because of the make up.
Big B wore specially designed dentures so as to effortlessly replicate the voice of a 13-year old child. 
He gets a lisp and his speech pattern gets height="300" src="cid:10.2414647210@web95406.mail.in2.yahoo.com" width="450">
He wore the dentures throughout the film's shooting and also had them on while dubbing.
Infact he has also sung a song in his voice wearing these dentures, which sounds like a child. 
But Big B never ever showed a sign of panic, on the contrary he was always co-operative, patient, cool and full of enthusiasm.
