The 36-year-old TV and radio personality was asked the "60 degree question" of "What's the most diva thing that you've ever seen Mariah do?"
"Have twins," Cannon replied, joking, "She shut the whole hospital down."
"When they was born, she made me play her music as they was coming out," he continued. "It was a fantasy. They was dancing...to "Fantasy."
Cannon and Carey share twins Monroe and Moroccan, who will turn 6 this weekend on what would have been the former couple's ninth anniversary.
Cannon has told the birth story before.
"Now my wife wanted to make sure that when the babies came out, that they came out not only to a Mariah Carey song, but a live performance from Mariah Carey—her Madison Square performance of 'Fantasy'—so they came out to a round of applause," he told Gayle King in 2011.
Cannon and Carey wed in 2008. He filed for divorce from in 2014 and it was finalized in 2016. Despite their split, the two remain the "best of friends," Cannon told Williams.
He and Carey have been hanging out more often in recent weeks, with their twins. Cannon told Williams he sometimes sleeps over at the singer's house, in their twins' room.
"Are you and Mariah still sleeping together?" Williams asked. "In my mind, you are and there would be nothing wrong with that."
"There would be nothing wrong with that," Cannon replied. "But that's not the case."
"There's nothing but unconditional love there," he continued. "I mean, she's gorgeous but, you know, I'm respectful. I put the kids to bed and I go home."
Williams joked that Cannon was the one who broke up Carey's subsequent relationships with two boyfriends, including ex-fiancé James Packer, who had taken her and the twins on vacation on a luxury yacht last year.
"I wanted her to be with the billionaire!" Cannon responded. "More yachts for everybody!"
"I'm just there to support my children," he added. "Whatever she wants to do with her personal life, I support her. I just want her to be happy."
He also talked about their split.
"I feel like when two people are in a relationship, it should be about growth," he said. "It should be a situation where everyone's becoming a better human being in the relationship. So when you get to a point where there's no longer any growth and you're not bettering each other...I felt like it was probably best, especially for our children, since they're the number one priority, if I could be the best human being and the best father from outside of that house."
"It was all my fault," he joked. "I did it."
Cannon recently welcomed his third child, a baby boy named Golden "Sagon" Cannon, with ex Brittany Bell. He said Carey was happy for him and that all his kids play together and visit him.
"It's all love," he said.