A one-hour special showing of `` The Secret of the Fire Nation '' which aired on September 15 , 2006 , consisting of `` The Serpent 's Pass '' and `` The Drill '' , gathered an audience of 5.1 million viewers .
A one-hour special showing of `` The Secret of the Fire Nation '' which was shown on 15 September 2006 , consisting of `` The Serpent 's Pass '' and `` The Drill '' , gathered an audience of 5.1 million viewers .