5. Keegan-Michael Key in the Icelandic Lava Field

As if right out of a science fiction movie, Bear Grylls swoops in on a jetpack to pick up funnyman Keegan-Michael Key, kicking off their adrenaline-pumping adventure in the lava fields of Iceland. The "Key & Peele" star must put all jokes aside to face some of his greatest fears and conquer the lunar landscape. From a perilous rappel off a sheer 200-foot cliff to an endurance-testing jumar climb, Keegan-Michael is pushed beyond mental and physical limits in a truly life-changing experience.