I've always loved Mythbusters and I'm usually happy with the way they do things.
One time, though, I think they got it wrong. The episode that I'm on about aired nearly a year ago, and I made a mental note to point out the inaccuracy. The myth was the revisited version of the one about fusing a hatchback between two big lorries in a crash, called "Compact Compact Supersized". The idea being that the two lorries crashing head-on would have enough energy to completely squash the little car.
Because it's so long ago, I don't remember the specifics, but it went ...