Sifu Kisu is the fighting instructor and consultant for the Avatar franchise. He is known for his extensive knowledge and abilities with various styles of martial arts. Sifu Kisu related the four bending arts to actual styles of fighting in real life, as to give bending in the series authenticity. His extensive work with the series is highlighted in the behind-the-scenes featurettes Creating the Legend and The Essence of Bending.
Bio Info: http://avatar.wikia.com/wiki/Sifu_Kisu