Sean Young was originally cast as Vicki Vale, but broke her collarbone while filming a horse-riding scene with 
Michael Keaton. The scene was subsequently written out of the script.
Willem Dafoe, 
David Bowie, 'John Lithgow' and 
James Woods were considered for the Joker.
 
Robin Williams was considered for the role of The Joker; he would later be considered for The Riddler as well. 
Jack Nicholson got the role of The Joker but demanded top-billing and a lucrative deal that gave him royalties on all merchandise.
 
Alec Baldwin, 'Charlie Sheen', 
Bill Murray, 
Pierce Brosnan and 
Tom Selleck were considered for the role of Bruce Wayne/Batman.
Mel Gibson was the original choice for Bruce Wayne/Batman but was forced to turn down the role due to his commitment with 
Lethal Weapon 2 (1989).
 
Michael Jackson was asked to write and perform the songs for the movie, but he had to turn it down due to his concert commitments.
 
Jack Nicholson received a percentage of the gross on the film, and due to its massive box-office took home around $60 million. As of 2003 it is still the single-movie record for actor's salary.
 
At one point, Warner Bros. considered doing the film as a big-budget comedy in the vein of the popular television series, with 
Bill Murray considered to play Batman, and 
Eddie Murphy considered to play Robin.
 
Jack Nicholson said of his role, "The thing I like about The Joker is that his sense of humor is completely tasteless."
According to Variety, 
Daniel Day-Lewis was considered for Batman/Bruce Wayne.