I'm hanging out at my classmate's house right now and her son is making a diorama of a forest for his science class. The trees he cut out look remarkably like celery and his mom commented as such. He looked a little sad, so I said "Don't worry about it. Celery is a sure sign you're in civilization."
He had no idea what that was in reference to, but he laughed and felt better.
Obscure "Doctor Who" references. I make them.