That’s right–someone actually for real turned down being part of one of the biggest franchises of all time. Interestingly enough, Sir Ian had a pretty good reason for doing so.
Apparently, the Harry Potter folks approached him after Richard Harris passed away. Harris played the headmaster of Hogwarts, Professor Dumbledore, in the first two films. They asked Ian McKellen to take over, but he just couldn’t do it.
“When he died–he played Dumbledore, the wizard–I played the real wizard of course,” he said in reference to his role as Gandalf in the Lord of the Rings films. “But when they called me up and said would I be interested in being in the Harry Potter films, they didn’t say what part.”
McKellen continued, “I worked out what they were thinking and I couldn’t. I couldn’t take over the part from an actor who I’d known hadn’t approved of me.”