Ken Allen wasn’t just any primate. The Bornean orangutan, born at the San Diego Zoo in 1971, became famous after a series of escapes in the 1980s. But he never went anywhere, and he never seemed to mind being led back into his enclosure—he just seemed to enjoy the challenge of finding a new way out! The “hairy Houdini” had a fan club, was the subject of T-shirts and bumper stickers, and even inspired a local folk song called “The Ballad of Ken Allen.” In an attempt to figure out how he escaped, the Zoo had staff members go undercover as tourists to watch him and even had rock climbers check out the walls. But even after they insisted there was no way to get up and out—Ken Allen found a way, once again. And still, he just hung around the enclosure, whiling away the time until the keepers came to lead him, quite willing to go, back inside.