Insane Inflatable 5k, Shelby Charter Township

In the Insane Inflatable 5K, a towering, albeit bouncy, staircase looks down on runners—and that's just the first obstacle. After clambering up one side and sliding down the other, contestants face a series of difficult grownup bounce houses with intimidatingly cute names. In the Waverunner, for example, participants meader up and down the undulating, wave-like runway of this 105-foot-long inflatable. Likewise, runners have to do high-knees for the 46 feet of Mattress Run, which tests their ability and balance as they must jump from ankle-deep hole to ankle-deep hole. The whole thing climaxes at the Finish Line, which features rubber wrecking balls, a human pinball machine of colorful bumpers, and a rope ladder. Afterward, everyone gets to head to the Insane Midway to enjoy carnival games, live DJ performances, and food and beverages.