The Dark Knight starred Ledger as the Joker.
 The Dark Knight features several cameo appearances, including Cillian Murphy, who reprises his role as Jonathan Crane / Scarecrow from Batman Begins; musical performer Matt Skiba; as well as United States Senator and life-long Batman fan Patrick Leahy, who has appeared in or voiced characters in other Batman media
 Christopher was confident in the casting because discussions between himself and Ledger had demonstrated they shared similar ideas regarding the Joker's portrayal

