The first American woman to go to medical school was admitted as a joke. Geneva Medical School thought it was joke when Elizabeth Blackwell applied to attend 1847. She graduated in 1849, started her own practice, and opened an infirmary for the poor.
In 2009, Burger King launched a campaign that if you unfriended 10 friends on Facebook, you were entitled to a free Whopper. The person you unfriended would get a message telling them that their friendship is worth less than a Whopper.