(CNN) It's not hard to make Jimmy Kimmel cry, and Ellen DeGeneres had him wiping his eyes.
The late-night host appeared Tuesday on "The Ellen Show," and his longtime friend surprised him by honoring Kimmel's infant son, William John.
Kimmel shared on his show in May that his son, known as Billy, had been born weeks earlier with a serious heart issue. The dad got emotional during a 13-minute monologue, using his son's health crisis to champion better health care and urge viewers to hold elected officials accountable.
Since then, Kimmel repeatedly has used his platform on "Jimmy Kimmel Live!" to speak out on the subject.
On Tuesday, DeGeneres thanked him for his advocacy.
"You're using your voice for good," she said. "You're saying a lot of important things."
Kimmel thanked DeGeneres and her viewers for raising $1 million for Children's Hospital Los Angeles, where Billy underwent open-heart surgery.
Then, DeGeneres told Kimmel she had a surprise for him.
"We called our friends at Children's Hospital L.A., including Billy's surgeon, and we have named one of the rooms of the heart institute floor in honor of Billy," she said.
"Wow!" Kimmel exclaimed a few times before wiping at his eyes.
DeGeneres then shared a look at the room via video as the surgeon and other staff waved. Meantime, some nurses who treated Billy were in the "Ellen" audience.
DeGeneres urged her viewers to visit her site and help raise another $1 million for the hospital.