The Rock's heartwarming message to young boy fighting cancer

The Rock serenaded Hyrum Harris (r) in character as Maui from Moana.

Global superstar Dwayne "The Rock" Johnson has taken time out of his busy schedule to bring some sunshine into the life of a Moana superfan who is battling an aggressive form of cancer.

Johnson posted video to Instagram to bring some cheer to Hyrum Harris, who fighting acute lymphoblastic leukaemia which is complicated by Down Syndrome.

In the video he delivers a message to the young fighter, telling him to "stay strong" and thanking him for "inspiring everyone around you, including myself".

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There’s a little 3 year old boy out there named, Hyrum Harris. Diagnosed with acute lymphoblastic leukemia which is complicated by Down Syndrome. In the fight of his life right now and doing his best to stay strong - by watching MOANA up to 10xs a day because the character he loves, MAUI makes him feel strong. According to Hyrum’s mama, his most important thing to say now is, I STRONG. Yes you are big man. Yes you are. Hyrum, I know I’m a complete stranger to you - who sounds a lot like your hero, MAUI (only with a very large head), but myself along with millions of other strangers who will watch this video are sending you so much love, strength and mana your way. I STRONG. Love, the Rock aka the dude who sounds a lot like Maui.

A post shared by therock (@therock) on Nov 18, 2019 at 7:52am PST

"This message is for a little boy out there, he's 3 years old, and this little boy is one of the coolest little boys around, and he's certainly one of the strongest because he is a fighter," Johnson says. "Right now, this little boy is in the fight of his life."

The star went on to say: "His name is Hyrum Harris. Hello Hyrum, I hope this message gets to you.

"You don't know me, my name is Dwayne Johnson, I also go by The Rock and you're probably thinking, 'Of course you go by the name of The Rock because you have a head the size of a rock!'"

Johnson then reveals that Harris watches Moana "almost 10 times a day" because the character of Maui gives him strength.

"People tell me I kind of sound like him," Johnson said. "I just wanted to send you a video to tell you how much I love Maui too. I know a little of his song."

Johnson then launches into 'You're Welcome', a hit song from the film.

He finishes by saying: "I wanted to tell you, man, stay strong. There's another dude out there, me, Dwayne, who, like you, loves Maui too. There's no one like Maui. He's the coolest thing. I'm a big fan of Maui, too, and I'm a big fan of yours. Thanks for inspiring everyone around you, including myself. Stay strong, Hyrum."

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Update from the video I posted. Look at this lil’ boy, Hyrum’s face. That’s some joy real right there. Thank you to the person who wrote this beautiful note. You’re absolutely right - joy and hope cost nothing and yet, is the most powerful gift we can give. Thats the real magic to life. #hopeforhyrum And thank you to my good buddy, Andy Fickman for texting me Hyrum’s story to begin with🙏🏾

A post shared by therock (@therock) on Nov 18, 2019 at 8:32am PST

After Harris and his family watched the video, Johnson returned to Instagram to share a note about the effect the video had on the young fighter.

The note read: "Joy and hope cost nothing, and yet it is the most powerful gift," saying that the video gave a boost to the whole family and medical team.

Harris' mother April told People magazine: "This has been such a moving experience for our family," adding that "every time Dwayne mentioned Hyrum's name, Hyrum pointed to his chest and in his soft sweet voice repeated saying, 'Hyrum,' as though he knew this was special for him," she added. "When he began to sing, Hyrum's eyes got very wide."