Dead Puppy Theorem

I have to say I stole this from a college of mine, Chris Lusto wrote a post about it:
http://linesoftangency.wordpress.com/2012/01/20/the-dead-puppy-theorem/

Dead puppy theorem: every time a student distributes an exponent to a binomial a puppy dies.  That is...

I introduced the idea during a warm up, and the students really liked it.  It always helps to throw up a picture like this:

would you kill this puppy?

Every so often a student kills a puppy: