On Wednesday’s Oprah, Brad Pitt tells the Queen of Talk that fatherhood has made him “hard as nails.”

“I’m impervious to poo, snot, urine, vomit,” the father of Maddox, Pax Thien, Zahara, Shiloh, and new twins Knox and Vivienne laughs. “You can’t get me. You cannot break me down.”

“Shiloh now only wants to be called John or Peter,” he explains. “It’s a ‘Peter Pan’ thing.”

Catch the rest of Brad’s revealing interview tomorrow on Oprah.