Chris Pratt Posts Adorable Video of Son Jack for World Prematurity Day

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Chris Pratt and Anna Faris' 3-year-old son Jack might have a career in show business just like his parents.

Jack's doting father posted a video of his little boy lighting up when his parents started to sing "ding dong, the witch is dead" from The Wizard of Oz. Wearing a bucket on his head while drawing, Pratt's son starts grinning from ear to ear when he hears the iconic tune.

WATCH: Anna Faris and Chris Pratt's Son Helps Name a Baby Penguin, and The Result Will Melt Your Heart

The Jurassic World star posted the video in honor of World Prematurity Day on Tuesday. "Premature birth is the leading cause of death in children under five worldwide," he told his 2.6 million Instagram followers. "About 15 million babies are born too soon every year. Nearly one million of these babies die within the first month of life. Support #WorldPrematurityDay and join the millions of volunteers who support #MarchofDimes."

This is a cause close to Pratt and Faris' heart as they welcomed Jack into the world in August of 2012, nine weeks before his scheduled due date. He weighed only 3 pounds, 12 ounces.

During the March of Dimes Celebration of Babies event in Dec. 2014, Pratt recalled the emotional moment that he first held his son. "I made promises in that moment about what kind of dad I wanted to be and I just prayed that he'd live long enough that I could keep them," he said. "Our Jack went from a small, helpless little squirt to a strong, smart, happy, funny, beautiful boy who loves monster trucks and Daniel Tiger, and, believe it or not, loves vegetables."

WATCH: Chris Pratt On His Son Jack -- 'He's Like My Therapist'

Pratt, 36, also opened up to GQ magazine about the birth of his son. "We were told, 'OK, you need to be prepared for raising a special-needs child,'" he recalled. "And we felt like it was devastating, but it also felt like, you know, 'We can do this.' He's alive."

WATCH: Chris Pratt Recites the Pledge of Allegiance With His Son and It's the Best Thing You'll See All Day!