"Daddy cries on TV, but Billy doesn't," Kimmel joked. "It's unbelievable."
Then Kimmel segued into an emotional monologue about CHIP, the Children's Health Insurance Program, which expired in October. Here's the transcript:
"We also want to thank the very bright and talented doctors and nurses at Children's Hospital who treated Billy, and not just Billy, many kids with so much caring and compassion. Children from every income level whose health is especially threatened right now because of something you've probably never heard of, it's called CHIP.
"CHIP is the Children's Health Insurance Program. It covers around 9 million American kids whose parents make too much money to qualify for Medicaid but don't have access to coverage, affordable coverage, through their jobs, which means it almost certainly covers children you know.
"About one in eight children are covered only by CHIP, and it's not controversial. It's not a partisan thing. In fact, the last time funding for CHIP was authorized was in 2015.
It passed with a vote of 392 to 37 in the House and 92 to 8 in the Senate. Overwhelmingly, Democrats and Republicans supported it. Until now.
"Now CHIP has become a bargaining chip. It's on the back burner while they work out their new tax plans, which means parents of children with cancer, diabetes and heart problems are about to get letters saying their coverage could be cut off next month. Merry Christmas, right?
"So this happened because Congress, about 72 days ago, failed to approve funding for CHIP since the first time it was created two decades ago. This is literally a life-and-death program for American kids.
It's always had bipartisan support. But this year, they let the money for it expire while they work on getting tax cuts for their billionaire and millionaire donors.
"And imagine getting that letter, literally not knowing how you will afford to save your child's life. This is not a hypothetical. About 2 million CHIP kids have serious chronic conditions.
"I don't know about you, I've had enough of this. I don't know what could be more disgusting than putting a tax cut that mostly goes to rich people ahead of the lives of children. Why hasn't CHIP been funded already? If these were potato chips they were taking away from us, we would be marching on Washington with pitchforks and spears right now."
Kimmel urged his viewers to call their representatives and "tell them to take a break from tax funds for a minute and fully fund CHIP immediately."
After a reminder to everyone to sign up for Obamacare ("In spite of President Trump's effort to sweep it under his rug, Obamacare is not dead, it's very much alive"), Kimmel turned the attention back to Billy.
"Billy is doing great, by the way. He has one more surgery," Kimmel said. "And this is amazing: He had an operation a week ago. They say he's probably on track to win at least a bronze medal in the Olympics in 2036."
Although Kimmel will likely get criticism for bringing his son on the air, the late-night host had a response ready in September - when he eviscerated the Cassidy-Graham health-care bill - for people who say he's "politicizing" his son's health-care problems.
"I want you to know: I am politicizing my son's health problems because I have to. My family has health insurance. We don't have to worry about this," Kimmel said at the time.
"But other people do, so you can shove your disgusting comments where your doctor won't be giving you a prostate exam once they take your health-care benefits away."
