Actor Ian McKellen has played a variety of roles in his long career, but two of his most iconic have been the mutant leader Magneto in the X-Men trilogy and the wise wizard Gandalf in the Lord of the Rings trilogy. McKellen is reprising the role of Gandalf in The Hobbit: An Unexpected Journey and The Hobbit: There and Back Again, the upcoming, two-part prequel to The Lord of the Rings, and it's hard to imagine anyone else in the role (thankfully, we don't have to for now). However, during an interview the December issue of Empire (via New Zealand Herald), however, McKellen revealed that he initially turned down the role of Gandalf.
How did mckellen end up as Gandalf? >>
At the time I was about to play Magneto in the X-Men film in Toronto. I was already committed to that ... and it meant I couldn't get to New Zealand in time. So I had to tell [writer-director-producer] Peter [Jackson] I could no longer do Gandalf.