The candid talk show host, 51, appeared on Conan on Thursday and shared this tidbit from her life as a mom: When Kevin Jr., at 13, walked in on her giving her husband a "favor" at 2 a.m.
"If you walk in on me and my husband, you're gonna get a surprise," she told host Conan O'Brien, adding of her son, "He got a surprise and he will never do that again."
"We don't close doors at our house," Williams said. "We walk hard in our house ... or we're always clearing our throats. That's the warning sign that 'here I come.' "
"He forgot to clear his throat and stomp!" she said.
Then she got to the must surprising part – at least for O'Brien. According to her story, when she and her husband noticed their son, they ... continued.
"You continued?!" the host said. "Wait wait wait wait wait wait, what do you mean you 'continued'?" (She meant exactly what she meant.)
And then: "The next day, he was going out with some of his friends and I usually, we leave the house with a hug and a kiss," Williams said, a grin forming. "We hugged, but he wouldn't kiss me!"