Mole Day celebrates something the scientific community calls Avogadro's number, which is 6.02 x 10^23. That's the number of particles (atoms or molecules) in a mole of something. (A mole is a basic unit of measurement.)
In eleventh grade, we could get extra credit for making something creative for Mole Day. I made a sock puppet of a mole (the mammal) who helped me give a brief talk about moles (the measurement) and Avogadro's number. He was pretty cute!
So, happy Mole Day, everybody! Science!