We love DARPA's unsettlingly-lifelike BigDog bot. We love it in spite of the fact that it's absolutely terrifying in motion. Now it has some bestial competition: the DARPA Cheetah. Ugh. Its legs. Its legs are so frightening.

Above, the Cheetah sets a speed record for four-legged robots, at 18 MPH. Herculean Olympian speed impossibility Usain Bolt can sprint at around 23 MPH. And he's a mutant of physical capability.

In other words, this thing can and will chase you down:

The robot's movements are designed to mimic those of fast-running animals in nature. The robot increases its stride and running speed by flexing and un-flexing its back on each step, much as an actual cheetah does.

The current version of the Cheetah robot runs on a laboratory treadmill where it is powered by an off-board hydraulic pump, and uses a boom-like device to keep it running in the center of the treadmill. Testing of a free-running prototype is planned for later this year.

DARPA won't elaborate on what the military applications of the Cheetah are—the BigDog is clearly for hauling heavy gear through rough terrain. So what will this metallic hell creature chase, someday, maybe? Terrorists? Bombs? If it can do more than run in a straight line, it'd be pretty killer for recon. Or imagine a hundred of them storming an enemy hideout at once on a suicide mission.

For now, its greatest capability is being extremely creepy to the point of being hard to watch. Why is it running backwards?