Billy was born to Kimmel and wife Molly McNearney in April with heart defects that required one surgery immediately after his birth, and a second surgery months later.
"I'm thrilled his son Billy's heart operation was a success. He's recovering very well", the actor announced during his monologue on Wednesday night.
"Jimmy and I can't go anywhere without someone coming up and thanking him for that monologue", said McNearney, who's also shares a daughter, Jane, 3, with the host. "He is eating, he is smiling".
"We're sending lots of love to all the Kimmels", Harris added. "He had 14 writers sitting in a room ready to write, and he said, 'I got this, ' and went into his own office and closed the door".
But, says McNearney, she had no idea how intensely personal his opening would be - or how he'd turn this monologue - and many afterward - into a rallying cry for congress to protect the Affordable Care Act for those less fortunate.
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Kimmel's infant son, Billy, had his third scheduled and successful heart surgery on Monday morning.
Pratt turned host on Monday with guests Margot Robbie and Chris Stapleton while Ross welcomed Mary J. Blige and Amanda de Cadenet on Tuesday night. Guest hosts like Harris will be filling in for Kimmel.
Since then, Kimmel has been very outspoken in favor of making sure Americans, especially those with pre-existing conditions, have access to medical care.
Jimmy Kimmel shared this photo of his son Billy on Instagram on October 21, 2017.
Little did McNearney or Kimmel realize, the remarks would strike quite a nerve in the public discourse as debate over health care was heating up at the same time.