It's a goofy, but catchy Korean pop song with a really strange music video that went viral a few months ago. The singer does this weird galloping dance maneuver throughout the video. Here's the original video.
It turned into this big meme to do parodies of the video. My favorite was shot at Dragon*Con earlier this month. Dragon*Con is a convention for genre geeks, so it's got all of these people in crazy costumes. I was at D*Con this year and even know one of the people in the video & remember seeing several of the others. If you only check out one parody I recommend this one.