John Stamos Reveals Son Billy's Nickname for Dad Is 'Poopy': 'His New Thing'

John Salangsang/Shutterstock John Stamos and his son, Billy Stamos

John Stamos says his preschooler is getting a lot of use out of his new favorite word.

The Big Shot actor, 59, appeared on Live! With Kelly and Ryan on Wednesday, where host Kelly Ripa and husband Mark Consuelos served as the day's hosts. During the chat, Ripa complimented Stamos on how he's taken to fatherhood.

"I have to say that in all the variations of John Stamos I've known over the years, watching you become a dad has been my favorite one," she tells the actor.

Admitting with a laugh that he "cries a lot," Stamos says his 4½-year-old son Billy, whom he shares with wife Caitlin McHugh, is the "light of our life."

Stamos then reveals that Billy's "new thing" is that he "likes to say 'poop,' all the time."

Stamos said Billy frequently says "hi poop" and one time, "I was trying to teach him a knock-knock joke" and he kept finding a way to insert the word.

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"[He goes,] 'knock, knock?' 'Who's there?' 'Poop.'"

The Full House alum recalls Billy asking him what the word appropriate meant, which the little boy used as an opportunity to talk about his usage of the word.

"I said, 'Well it's not appropriate to say 'poop' at school or talk about poop at school,'" Stamos says.

"He said, 'well what if I go to a poop school?'" Stamos says with a laugh, adding, "he's smart."

Stamos also shares that during a recent FaceTime call, he was saying goodnight to Billy and told him to go look at the moon while he, who was away from him that night, did the same.

"And then he said, 'Daddy, I can see your eyes in the moon,' and I said, 'Son, I can see your eyes too.' It was that beautiful moment, and I said, 'I love you, Billy.'"

Equally heartfelt, Stamos says Billy responded, "I love you poopy."

John Stamos/Instagram

Speaking with PEOPLE at Cool Comedy * Hot Cuisine's Tribute To Bob Saget last month, Stamos talked about the "enduring legacy" of Full House, noting that Billy has taken to watching it himself.

"Today, my son is home all day and he's watched it," he recently told PEOPLE, joking, "sometimes I come home and the nanny is showing it to him and I'll fire her and I'll put him on time out."

Stamos said Billy has already taken to the show's many catchphrases, noting, "He'll sarcastically give me catchphrases like 'You've got it dude.'"