Michael J. Fox has just turned 60 years old, and thousands of fans are paying tribute online. Fox, who announced his retirement from acting last year, first rose to fame by playing popular teenage characters in the 1980s. After breaking out as Alex P. Keaton on the classic sitcom Family Ties, he landed the iconic role of Marty McFly in the Back to The Future series, forever becoming one of Hollywood's most beloved stars.

Fox announced his Parkinson's disease diagnosis in 1998. Though he continued to perform, the actor became an advocate for finding a cure. He founded the Michael J. Fox Foundation in 2000 to help fund research into curing the disease. In his memoir No Time Like the Future, which was released in November, Fox addresses how his declining health led to his recent retirement from acting.

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In honor of his birthday, thousands of fans are honoring Fox. Recognizing his role as Marty McFly, one fan said, "Here's something to think about. Today Michael J. Fox is 13 years older than Christopher Lloyd was when they filmed Back to the Future. Happy 60th Birthday #MichaelJFox. For me, you will always be the coolest teenager on film."

"Happy Birthday to both Marty McFly and Michael J Fox," says another fan, including an image of Marty McFly's ID. "He's one of my favorite celebrities who has yet to disappoint me. Happy 60th."

Another fan says, "Michael J. Fox was my celebrity crush for all of my childhood. The fact that he has turned out to be an incredible man gives me hope that maybe my instincts are right, after all. Happy 60th Birthday, Alex P. Keaton."

"Happy birthday Michael J Fox!" says someone else. "Yes, Back to the Future will always be the most memorable film, but it's your role as Alex P. Keaton, especially in 'A, My Name is Alex', that always hits the hardest for me."

In the Back to the Future video game from Telltale Games, Fox voiced Marty McFly's great grandfather William. Recognizing the game and Fox's cameo, one fan posted: "Since it's Michael J. Fox's 60th birthday, I feel it only right to post about it given how much I loved Back to the Future as a kid. I loved how, in the Telltale game, he cameo'd in the final episode which surprised me given I didn't expect to hear him at all in that back then."

Another tweet reads: "Happy Birthday to one of the most kindest and amazing human beings in this planet Michael J Fox u are an inspiration for many, ur strength, ur courage and ur love for life is one of a kind We love u beautiful boy Thank u for all the joy u have bring to us."

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And another fan said, "As it's #MichaelJFox's 60th birthday, let's acknowledge that one of the few things we as a global community agree on is that Back to the Future should never be remade, and that's entirely because no one else can ever play Marty McFly. Happy Birthday @realmikefox ! We all love you."

Let us also join the rest of the fans by wishing Fox a very happy 60th birthday! You can see what many other fans are saying about the actor's special day on Twitter, and you can find out more about Fox's search for a cure by visiting the official website for The Michael J. Fox Foundation for Parkinson's Research.