On Halloween you better hide your candy, or else there will be a fella named Big Dick Randy.
Big Dick Randy
Explanation
Explain Bear
Listen up, buttercup. This joke is about Halloween and a dude named Big Dick Randy. The joke suggests that you should hide your candy on Halloween or Randy will take it. It's funny because it's unexpected and uses a crude name for shock value. I bet your candy is hidden because you eat it all!