Christopher Lloyd, who played Doc in the legendary film trilogy, has said he would be up for making Back to the Future: Part IV.

"I would love to do Doc again, no question," he said in an interview with The Hollywood Reporter. Though he admitted there are a few challenges that would present themselves in making another.

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"It's tough to come up with an idea that contains the excitement of the original three," he explained.

"So it would be a real challenge for the writers to come up with an original Back to the Future story that has the same passion and intensity and excitement as the other three. But it could be done, you never know."

And despite Michael J Fox's well-documented Parkinson's disease, Lloyd thinks he would love to get involved.

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"I think regardless of the Parkinson's, he'd probably jump on the role and he'd be great," Lloyd said. "I can't see doing another sequel without him. I would certainly want Bob Zemeckis directing it, Bob Gale writing it and the other principals being involved."

"It's hard to replace Marty," he added. "Michael J Fox was so wonderful in the role. He's just so great to see. He's just so warm and smart and has such courage coping with the Parkinson's. He's indomitable. He's just great to be around."

And thinking of the franchise as a whole, Lloyd admitted he still is blown away by how successful it has been for all this time.

"I'm surprised. I had no anticipation that it would still be so popular. It hasn't faded."

From: Digital Spy