A kangaroo kept getting out of his enclosure at the zoo:
Knowing that he could hop high, the zoo officials put up a ten-foot fence.
He was out the next morning, just roaming around the zoo.
A twenty-foot fence was put up. Again he got out.
When the fence was forty feet high, a camel in the next enclosure asked the kangaroo.
“How high do you think they’ll go?”
The kangaroo said.
“About a thousand feet, unless somebody locks the gate at night!”