When Michael J Fox was included in Time‘s 100 Most Influential People list on Thursday, there was no one better to write about the Back to the Future star than Ryan Reynolds.

The Deadpool actor, who has served on the Michael J. Fox Foundation for Parkinson’s Research board since 2009 – wrote a candid and moving passage about his friend and the effect he has had on his own family.

“I know Michael J. Fox. Like, I know him pretty damn well. He’s funny. He’s warm. He’s handsome and intensely smart. He also falls a lot. Not just because he has Parkinson’s,’’ Reynolds wrote.

“He falls a lot because he’s unafraid to fly.”

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At just 29, after noticing a tremor in his little finger, Fox, 62, was diagnosed with young-onset Parkinson’s disease a year after Back To The Future Part III was released in 1990.

He hid his diagnosis for years and continued in Hollywood.

After going public in 1998, he was approached to join other Parkinson’s foundations.

Angered by the competition for a disease that continues to search for a cure, he founded the Michael J. Fox Foundation for Parkinson’s Research in 2000.

It has since produced more than $US2 billion ($3.1 billion) in funding and is dedicated to research and therapies, reportedly giving more money than the US government.

“It’d be kinda lazy to simply characterise him as the greatest champion of Parkinson’s research on the planet,” he continued, praising the star for his decades of philanthropy.

Reynolds wrote that Fox helped his late father, who had lived with Parkinson’s for nearly 20 years – and millions of others, “feel less alone”.

James Reynolds, a Royal Canadian Mounted Policeman, died in 2015 aged 74, reported People.

“He’s someone who helped my dad, along with millions of others, feel less alone.

“It’d be kinda lazy to simply regard him as a movie star who shaped the lives of people all over the planet with a uniquely electric wit and self-aware charm.

“He’s the sum of these beautiful parts,” said Reynolds, who is known for he and his wife Blake Lively’s international charity work.

Michael J Fox and Ryan Reynolds at a benefit for the Michael J Fox Foundation in 2008. Photo: Getty

One of 16 ‘icons’

Fox falls into the “icon” category in Time’s annual 100 most influential list, joining 15 others including Australian pop sensation Kylie Minogue.

“Kylie creates a space where everyone is safe to be themselves. When I look at her I feel hope. She’s proof there are humans who don’t judge,” wrote Coldplay’s lead singer Chris Martin in his Time passage.

Jenni Hermoso is another icon who spoke up after Spanish football boss Luis Rubiales grabbed her face and kissed her on stage after the Women’s World Cup final in Sydney.

There’s also categories for artists including award-winning actor Da’Vine Joy Randolph (The Holdovers), Titans (F1 driver Max Verstappen), leaders, innovators and pioneers.

Earlier this month, Fox was front and centre at another foundation benefit, flanked by musician Sheryl Crow and wife Tracy Pollan. Photo: Getty

Earlier this year, Still: A Michael J. Fox Movie was released. It documented the actor’s life with Parkinson’s disease.

Fox shares four children – Sam, Schuyler, Esmé and Aquinnah – with wife, 63-year-old US actor Tracy Pollan. The couple had been married just three years when he was diagnosed.

In February, he told Entertainment Tonight he would consider acting again “if I could figure it out”.

“If someone offers me a part and I do it and I have a good time, great,” he said.

“I would do acting if something came up that I could put my realities into it, my challenges, if I could figure it out.”

He said his goals were always shifting, but his biggest goal had been “to raise a family” with Pollan.