BAD JOKE TIME ... AGAIN

I am well known at my work for telling groaners. I always keep them clean--have to maintain that PC motif--but most of my staff moan after I tell a joke. Okay, sometimes they stare at me with a blank expression then ask for an explanation. Anyway, I'm going to share my latest:

A little boy was looking at his mother and noticed she had a few white hairs among her dark curls. He asked, "Why do you have some white hairs?"

Mom looked over at him. "I get white hairs every time you scare or upset me."

He nodded, accepting the answer, then suddenly his eyes grew large. "What did you do to Grandma?"