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Jimmy Kimmel donates 1,000 masks to Children's Hospital Los Angeles to mark son's 3rd birthday

Children's Hospital LA treated his son, Billy, as a newborn.

In honor of their son Billy's third birthday, the "Jimmy Kimmel Live!" host paid it forward to the staff at Children's Hospital Los Angeles on Tuesday.

"Happy 3rd birthday to our sweet & strong Billy. Thanks to the heroic doctors, nurses & respiratory therapists who saved his life & countless others," tweeted Kimmel, who also posted an adorable photo of his son dressed up as a very buff Spider-Man.

In order to alleviate the pressure on hospital staff, Kimmel further announced, "My wife @MollyMcNearney & I are donating 1,000 masks to @ChildrensLA."

He also revealed that fans who support the doctors and nurses at the Children's Hospital will have their donation matched when they visit the hospital's website.

Shortly after Kimmel made his announcement, the hospital thanked the late-night host by sweetly writing back, "Happy birthday Billy!!! Many thanks Molly and Jimmy for always thinking of us."

Billy was diagnosed soon after birth with Tetralogy of Fallot with pulmonary atresia, a congenital heart defect, and had surgery at Children's Hospital Los Angeles when he was just 3 days old -- a harrowing journey Kimmel tearfully relayed to fans during an opening monologue in May 2017.

Seven months later, Billy had to undergo yet another lifesaving surgery.

Now, the toddler is a healthy and happy 3-year-old who enjoys eating Pasta Tina with his big sister, Jane.