Michael Keaton nearly played Jack on LostS

In the early days of Lost's development, the creators had a very different idea for the character of Jack: first, he would die in the pilot episode; second, he would be played by Michael Keaton.

J.J. Abrams initially approached Keaton about the idea of playing Jack, and Keaton was intrigued by the idea of doing the television pilot. Jack would die in the first episode, giving Kate more of a leadership role in the full series. However, once it was decided that Jack would be spared, Keaton decided not to take the part. In a 2005 Access Hollywood interview, he explained:

Keaton says he was thinking about doing it until Abrams called to let him know that "Dr. Jack Shepard," who was slated to die in the first episode of the original pilot, would instead be a series regular. "I said, 'I'll seriously consider it, send me the script,'" says Keaton. "He said, 'No, we're keeping the guy alive,' and I said, 'Oh, ok, well I can't do that.'"

Despite the success of "Lost," Keaton says he knows he made the right decision. "I wouldn't do it if the guy was going to be in the show every week," he says. "An hour show every week... I've got stuff to do, I've got a life to lead. When would I fish?"

Michael Keaton Reveals Why He Passed on 'Lost' [Movie Insider via Blastr]