This is the same group that did the "5 Peeps 1 Guitar" video -- they sometimes make little short-films to further promote their videos. Apparently they have a short-film in the works for this song as well. I'm curious to see what they'll come up with!
Student (drinking from a mysterious cup): "Where am I? What is this?"
Teacher: Urin...
Student spits
Teacher: ...my dojang.
Off topic of tkd, but this one is my favorite because of how challenging it must have been to make - they must have been lip-syncing REALLY FAST in real-time, in order to get the audio to still match after the video was slowed down.