At the 2012 X-Games, Hot Wheels attempted a death-defying, double loop. Unlike when you were a kid and actively trying to destroy your toy cars, though, this was a life-size attempt, with real drivers behind the wheel. The massive stunt, with two 66-foot-tall loops, was completed by Tanner Foust and Greg Tracy, and now there's a short YouTube documentary on the process involved in setting up the stunt.
It shouldn't be a surprise, but there were crashes in practice. Hot Wheels rigged up a poor Mitsubishi Lancer Sportback with a remote-control system as a practice vehicle, which eventually pancaked itself into the track midway through its run. The full-size RC car showed the lengths that the team went to get this stunt right, while making it as safe as possible for the two drivers.
You can check out the complete documentary below, along with the live lap from the 2012 X-Games in Los Angeles.