"I was going to Israel last week, it was my first work trip for '60 Minutes' and I was doing an interview," began Cooper, 54. "I get this text from Wyatt's other dad, Benjamin, and he said, 'He just walked!!'
"My reaction was fury," he jokingly continued. "I was like, A. I can't believe I missed this [and] that I'm doing this interview in Israel of all places."
"Secondly, then I got really pissed at Benjamin," Cooper added. "In my household when I grew up, you would lie about everything. He should have just lied. He should have lied and said, 'Oh no, he's not walking at all so when I got home and he walked, we'd be like, 'Oh my god! It's the first walk.'"
Colbert, 57, assured Cooper that missing his child take his first steps "proves" he's a father.
"He walks like a drunken sailor," Cooper quipped in response.
The "AC 360" host also pointed out that Wyatt -- whom Cooper named after his father -- has also started talking.
"He talks in a dialect of Hindu or Urdu, I'm not sure," Cooper joked. "It's incredible. It's a really interesting dialect. He doesn't make any sense at this point, but he's really committed to it."
The "60 Minutes" host went on to share his thoughts on his second Father's Day as a dad, admitting that he forgot the holiday was coming up.
Cooper said that since his father passed away when he was 10, he often "avoided" and didn't "acknowledge" Father's Day growing up.
"The pain was so great for most of my life I didn't know Father's Day was this date," he told Colbert, whose father also died when he was 10.
The journalist said fatherhood has connected him with his late family members.
"And yet, the interesting thing about having a child is it's made me sort of connect with my dad and my mom's past and my brother's past in a way that I never really anticipated," he explained.
"I feel like I'm in communion with them in some strange way," Cooper continued. "I remember things about my dad that I never remembered before because I'm experiencing them with Wyatt as a dad."
Cooper added that his late mother enjoyed painting and made a portrait of herself and his father. Cooper said that he hung the painting outside his son's room and became emotional when he revealed that Wyatt has a connection to the portrait.
"Every morning when I walk by, he stops and he insists on going over and touching the portrait of my mom and my dad, which I find really wonderful," he said, voice cracking.
Cooper and Maisani welcomed son Wyatt in April 2020 via surrogate. The former couple is raising the child together even though they split in 2018.
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