Ledger documentary reveals secret behind Joker's lip-licking

The documentary on the life of actor Heath Ledger has disclosed that a make-up issue was responsible for The Joker's menacing lip-licking habit in "The Dark Knight".
"I Am Heath Ledger" revealed the Australian actor had to wear a prosthetic scar to play Batman's arch rival which would often come loose, reported Elle magazine.
Ledger secured the make-up by constantly licking his lips. This ended up becoming one of the many details that made his Joker appear even more dangerous.
The actor was 28 when he died of a cardiac arrest brought about by combined drug intoxication on January 22, 2008.

The documentary will receive a digital release on May 23.