Math Jokes or Thoughts of the Day

I know many teacher's who put up little riddles, brainteasers or thoughts of the day to engage their students when they walk into the classroom.  Here's a great site that could give us a lot of material to do this in a math classroom. 

http://www.math.utah.edu/~cherk/mathjokes.html

This is my favourite one:

Top ten excuses for not doing homework:

• I accidentally divided by zero and my paper burst into flames.
• Isaac Newton's birthday.
• I could only get arbitrarily close to my textbook. I couldn't actually reach it.
• I have the proof, but there isn't room to write it in this margin.
• I was watching the World Series and got tied up trying to prove that it converged.
• I have a solar powered calculator and it was cloudy.
• I locked the paper in my trunk but a four-dimensional dog got in and ate it.
• I couldn't figure out whether i am the square of negative one or i is the square root of negative one.
• I took time out to snack on a doughnut and a cup of coffee.
• I spent the rest of the night trying to figure which one to dunk.
• I could have sworn I put the homework inside a Klein bottle, but this morning I couldn't find it.
Warning! It is against the rule to use these excuses in my classes! A. Ch.