Hospital scene

In The Dark Knight, during the hospital scene Aaron Eckhart spoke about a unique experience he had with Heath Ledger. He said that before lines were exchanged, Ledger would just walk around, in character, mumbling to himself in an odd manner. All Eckhart could do at the time was just watch him while still in character. This went on for several minutes, until Ledger got close to him. Eckhart felt compelled at this point to fiercely raise his hand up. Immediately, Ledger grabbed Eckhart's raised hand in an equally matched fierce manner. When the scene was over, Ledger, now out of character, told Eckhart “That's what acting's all about.”