Dr. Phillip Thrush promised Austin - a die-hard Star Wars fan from Pontiac, Illinois - that when a heart became available, he would deliver the good news wearing a Chewbacca costume.
Dr. Thrush made good on his promise Saturday, speaking fluent Wookie. The heartwarming moment was captured on video in Austin's room at Lurie Children's Hospital in Chicago.
RAW VIDEO: Chewbacca tells boy he's getting a new heart
"We got a heart? Do we seriously have a heart?" Austin asked before high-fiving and hugging the pediatric cardiologist-turned-Wookie warrior.
"To see him knowing that he has a chance at life, that he has a chance to achieve so many things leaves you speechless," said Austin's mom, Mary Anglin, of that blissful moment Saturday morning, which has more than 70,000 views on Facebook.
Anglin also expressed gratitude for the donor's family, which had to make a courageous decision to donate a child's heart in their time of grief.
"He will make sure that he does remarkable things because of it," Anglin promised.
First up: lobbying Marvel to host a special screening of Avengers: Infinity War for the Lurie's kids who cannot leave the hospital because of their illnesses.
He's started a social media campaign using the Twitter handle @TheReelThanos, hoping to get the movie maker's attention.
Marvel and ABC11 are both owned by the Walt Disney Company.