The story behind PK's title

At one point in the film, PK says,"Naam kucho nahi hai hamaar, lekin pata nahi kaahe sablog hamka Pk-Pk bulwat hai". Why?

The film was initially titled Tully, Hirani reveals, "It felt too slangy, so we decided to call it PK. Wherever Aamir's character went, people kept calling him PK. He goes to the police station to file a complaint against God, and the policeman asks, ‘Peeke hai kya?’ Then he goes to a temple and asks for his donation back, and again, someone says, ‘Pi ke aaya hai kya?’ That’s when his character begins to think that PK is his name. The idea was to make him seem drunk because the things he was saying were so absurd. For instance, going to the police and saying, ‘I want to file a complaint against God; he’s taken my money but hasn’t done the work.’ Anyone would think, What? Are you drunk?"

"But the character speaks with innocence. He says, ‘Main donation mein paisa daal raha hoon, lekin mera kaam nahi kar rahe bhagwan. Kaam nahi karna hai toh wapis karo mera paisa.’ That was the reason behind naming him PK," Hirani explains.