In an article from The Hollywood Reporter, they recount an interview they had with Sir Ian McKellen on the set of The Hobbit as he talked about how he almost didn't return to the role of Gandalf.

"It was a little like going back to something that wasn’t necessarily going to be particularly challenging. Gandalf is still inside me, as it were, so the business of getting to know a new character -- I was sort of going to be robbed of that. You felt, how many millions of people are waiting for it? They wouldn’t understand if you weren’t as keen as they were."

"Peter Jackson and I much prefer Gandalf the Grey, who was a man who did manage to enjoy himself,” McKellen says. In fact, McKellen seems to be the impish one on the set, clowning and mugging between takes. But he knows it’s important to take the quest seriously. “I was joking around and one of the other actors said, `Stop it, Ian,’ " McKellen says. "And he was quite right."

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