"The Watermelon Patch" joke
A farmer who grew watermelons was troubled by some local kids. Each night, the kids would sneak into his watermelon patch and eat the watermelons.
After some careful thought, he came up with a clever idea to scare the kids away. He made up a sign and posted it in the field.
When the kids showed up the next night, they saw his sign: "Beware! One of the watermelons in this field has been injected with cyanide."
So, the kids ran off, made up their own sign and posted it right next to the farmer's sign.
When the farmer came to check his field in the morning, he was relieved to see that no watermelons were missing. Then, he noticed the new sign next to his:
"Now there are two!"
Not enough votes...