http://www.youtube.com/watch?v=2rCUi3edATo&feature=vmdshb

If you guys have the time,may you kindly watch the video and tell me whether there is something wrong?Well i was playing in a server and this happened.I really have no idea what this is.Is it something special or is it a hack?If you guys have the time may you please kindly tell me what is it.I would really appreciate it.Thanks alot guys