Back story: Thursday night, my dog got out of the yard (surprise) and I spent the evening trying to track her back down. I finally found her, having cornered a squirrel halfway up a tree. Sadly, she had managed to injure the poor critter, and it's shoulder/arm was seriously mauled, to the point where it couldn't climb anymore. I was traumatized, and shared the story with my first period the next day.

Student: Hey, I have a riddle! What has 1 foot on one end, one foot on the other end, and a third foot in the middle?
Me: I don't know, what?
Student: A yard stick!
Student #2: Or the squirrel from last night.

Touche.