The big man was taking a shower after a basketball game on the set of their new movie Grown-Ups 2 and Sandler decided he had to find out how big his co-star's manhood was.
He says, "Everyone else left and I'm like, 'Ok, let me see that thing...' I go back there... and his bodyguard is there and his bodyguard is just so strong... so I said, 'Sorry, I was just trying to see Shaq's penis... I'm outta here. Please don't tell Shaq this happened.'
"I see Shaq later on the set and I guaranteed that guy ratted me out, so I said, 'I'm sorry about that before with your security guard,' and he said, 'I don't have a security guard, that was my d**k!'"