"Back to the Future Part II"
We already knew Marty McFly (Michael J. Fox) was an ace skateboarder thanks to ‘80s hit “Back to the Future.” But when the sequel plopped him down in 2015, he proved far less adept at the hoverboard—a wheel-less skateboard that floats and flies a safe(-ish) distance above the ground.
Real-world potential: Any hovercraft invented thus far still has a cushion of some kind connecting it to the ground, unlike the totally unfettered hoverboard. So anyone expecting hoverboards in the next four years will have to settle for Marty’s shoes instead.