John Stamos’ 4-year-old son Billy has a very interesting nickname for him.

Stamos welcomed Billy with wife Caitlin McHugh after they married in 2018.

He called his son the light of his life.

Stamos said Billy was obsessed with saying the word “poop.”

He said the 4-year-old includes it in knock-knock jokes.

Stamos talked about facetiming his son Billy while on “Live With Kelly And Ryan.”

Billy referred to him as “poopy” towards the end of the call.

Stamos said his relationship with his younger “Big Shot” costars impacted how he raised his son.

He plans on raising Billy to be loving and kind.