Sorry, couldn't resist...... The Lincoln Park Zoo ape house was a state of the art facility when constructed in the late '70s. One of its features was an outside play area that different species could access on a rotating basis. The play area had high acrylic and concrete walls, too high for any of the apes to surmount. At least, in theory..... In 1983 or so, one of the gorillas got curious about the world outside. Apparently the zoo designers had underestimated the leaping ability of gorillas. The male leapt high enough to get a hand on the acrylic wall's top. From there he swung over the wall and landed in front of a Hispanic family who'd come to see the apes. They took off. The male gorilla then went for a stroll, getting a closer look at some of the other enclosures visible from the ape house playground. He acted every bit the considerate zoo visitor, although the human zoo visitors were probably torn between wonder and panic. After a few minutes, the zookeepers came by with a tranquilizer gun and ended the Ape Escape. Needless to say, the walls were extended higher.