Ledger, whose death Jan. 22 death in his New York apartment has prompted numerous rumors, intensely prepared for his "Knight" role by locking himself in a London hotel room, the New York Post reported .

The 28-year-old actor reportedly spent six weeks in the hotel room perfecting the mindset and mannerisms he would use in the role.

This experimentation included practicing laughs and voices that would help him bring the famed "Batman" villain to life on the big screen.

Ledger even created a journal filled with Joker-based thoughts, including a page of things the fictional arch-villain would find humorous.

Among those items written on the troubling list was "AIDS," the Post reported.

Ledger's performance in "The Dark Knight" can be seen July 18, when the expected blockbuster premieres.