This may have come from TM a year or so ago. I thought of it because I am on a cruise close to the Antarctic and will be seeing Penguins for the next few days:
Bloke walks into a police station and asks the desk sergeant "Can you tell me, how tall is a penguin?"
The desk sergeant looks at him, puts down his pen, folds his arms and says "About two foot tall sir".
The bloke considers this, then asks "So how tall is a king penguin?"
The desk sergeant thinks for a second, and replies "I reckon about two foot six sir"
The bloke considers this for a short time, then ask "So how tall is an emperor penguin?"
The desk sergeant had to think of this, but being a wise man he responded "I reckon the tallest one recorded must have been in the region of three feet tall sir".
The bloke considers this fact, then looks the desk sergeant in the eye and says "in which case I have to report the fact I have run over a nun..."