Appliance of Science: What's the funniest joke you've ever heard?

...and what's the formula for humour?

According to a year-long survey, including more than 1.5 million people, the duck is considered the funniest animal.

Dad jokes, bad jokes and side-splittingly funny jokes. What defines the good from the bad? What is the best joke you ever heard and would science agree with you?

The funny side of sadness