He's No Houdini

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. Again the kangaroo was out the next morning, just roaming around the zoo. So the fence was extended to twenty-foot. But the kangaroo was out the next morning.

Frustrated the the zoo officials built a fence forty feet high. A camel in the next enclosure asked the kangaroo, "How much higher do you think they'll go?"

The kangaroo said, "About a thousand feet. Unless somebody locks the gate at night!"