The host congratulated the 31-year-old actress on her new daughter Wyatt, who she confirmed is "two months, nine weeks."
"She’s not lethargic. She moves!" Mila said of her baby.
Craig made a comment that girls are easier to raise then boys until they become teenagers. Mila quipped, "That’s not my problem. That’s daddy’s problem!"
She added regarding the birth of Ashton's sister Tausha's son in September, "My sister-in-law had a little boy two weeks prior to us having our little girl and it is completely different. Everything."
"Sister-in-law"?! Did Mila secretly marry Ashton?!
The former That 70s Show star already seemed to have dropped her baby weight as she stepped out wearing a sexy, short black dress (LBD). She credited her weight loss to breastfeeding.
Mila -- who called the Late Late Show her "favorite show in the world to do" -- and Craig both have Scottish roots, and when asked if she plans to raise her baby Scottish, the actress responded "absolutely." In fact, she even bought Ashton, 36, a kilt.
"It turned out great, because you know, nothing’s under the kilt," she said. "He loves kilts. The day that I landed, when we got back from Scotland, was on St. Patty’s Day. And then we went out to a bar and he wore his kilt and now every St. Patrick's Day."