From the ArcaMax Publishing, Jokes Newsletter:
http://www.arcamax.com/news/jokes/s-573493-909238
My 4 year old son came screaming out of the bathroom to tell me he'd
dropped his toothbrush in the toilet.
So I fished it out and threw it in the garbage.
He stood there thinking for a moment, then ran to my bathroom and came
out with my toothbrush.
He held it up and said with a charming little smile, "We better throw
this one out too then, 'cause it fell in the toilet a few days ago.