Dwayne Johnson sends message singing 'Moana' song to 3-year-old battling leukemia

Dwayne "The Rock" Johnson just got back into one of his former characters for a very special boy who is battling cancer.

The actor shared a video on Monday singing "You're Welcome," the hit song his character, Maui, made famous in "Moana" for 3-year-old Hyrum Harris from Woodstock, Georgia.

The little fighter was diagnosed with acute lymphoblastic leukemia on Oct. 20, 2019, and has been hospitalized at Children's Healthcare of Atlanta at Scottish Rite since then.

His mother, April Harris, said his treatment has required a lot more care because of his Down syndrome. "Hyrum has had health challenges for most of his life," she told "Good Morning America." "We've been in the hospital time and time again. He has multiple illnesses -- asthma, epilepsy, Chronic Croup, FPIES and some GI stuff as well."

One thing that's helped him during his time in the hospital? Watching "Moana."

Harris has shared how much the film has helped her son in her daily blog posts, which she writes in order to keep family and friends updated on Hyrum's condition.

"One day I posted about when Hyrum's sick he watches 'Moana,' when he's sad he watches 'Moana,' when he doesn't have strength he watches 'Moana' and when he's happy he watches 'Moana' -- because it's become this coping mechanism to help him get through the very hardest of days," Harris explained.

Her best friend from high school, Micaela Brown, saw her posts mentioning "Moana" and asked if she was okay with her reaching out to Johnson's team, which Harris agreed to. The family was shocked when Harris received a video a few days later from Johnson.

The actor also shared the video on his own Instagram account, with a sweet message for Hyrum.

"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," Johnson wrote in his post, featuring a video devoted to Hyrum.

In the video, he described Harris as, "one of the coolest little boys around," adding that he is, "certainly one of the strongest because he is a fighter."

"I heard that you love a movie called 'Moana,' which is crazy, because I love that movie, too," he said directly addressing Hyrum. “And I also heard that you watch ‘Moana’ almost 10 times a day because the character you love, Maui, gives you strength."

He shared that he thought it was "so cool" that Hyrum found strength through Maui and revealed, "people tell me I kind of sound like him."

"I just wanted to send you a video to let you know how much I love Maui, too...I love Maui so much I know a little bit of his song," he added before singing the hit from the 2016 Disney film.

Harris said her son had a "beautiful" reaction to the video.

"Hyrum's not completely verbal. He's three, but developmentally he's much younger because of his Down syndrome," she shared. "There's some words he can say, and one of them is his name, so when Dwayne Johnson said 'Hyrum Harris', Hyrum pointed to himself and put both hands on his chest, almost like he's like a gorilla, and said to himself, 'Hyrum, Hyrum that's my name!'"

"It was this moment where Hyrum knew this really special thing had been done for him," she added.

She said Johnson's gesture also helped her other children, as Hyrum is one of seven.

"Everybody needs something to push through, and Hyrum may not know who The Rock is, but I guarantee that my 12-year-old and my 16-year-old do, who are trying to go to school every day with their peers and their teachers saying 'how's your brother today?'" she said.

"They lose a sense of themselves -- and knowing that somebody like The Rock would reach out to our family and leave a message for Hyrum, it gives you enough strength to get through."

Micaela Brown also shared a note describing the impact of Johnson's gesture, which he later reposted.

"April said Hyrum watched it and laughed out loud at The Rock's head, and every time Dwayne said Hyrum's name pointed to himself and giggled," Brown posted.

Her note touched on how much Johnson's video impacted those in Hyrum's life as well.

"Hyrum loved the video, but the family who is up all night working through medication with the baby, the nursing staff caring for all the sick children on the floor, the family across the USA who can't be there in person - ALL were given a boost - that they aren't alone...and if they need a little help, they can borrow strength from The Rock," her note continued.

Johnson agreed with the sentiment expressed in the note, and captioned his shot of the message, "Joy and hope cost nothing and yet, is the most powerful gift we can give. Thats the real magic to life."

Harris said she wants the world to know that her Hyrum is "just the sweetest little 3-year-old boy that housed the spirit of a lion and and the heart that makes the world okay."

She said she's also overwhelmed by the interest in her son's story.

"Something as sweet as a three minute video has made ripples," she said. "It's been a beautiful thing for our family and I think for the nation to remember that people need prayers and love and support more than they need anger and anxiety."