"(Bale) would be in the corner somewhere, with his eyes closed and his head propped on a set piece. Sometimes he'd fall asleep," Contactmusic quoted Mangold, as saying.
"You'd almost think he's narcoleptic. But, in reality, I think it's a way he stays focused," he added.
But Bale eventually cleared the concerns by explaining that it was his method of preparing for the next scene.