I was watching some old episodes from book one when i picked up on something i hadn't before. When Aang accidently goes to the Spirit world the first time and is guided by Roku's Dragon...No one can see him. But while IRoh was captured by the Earth Kindom soldiers and he was chained up on the back of their Ostrage Horse he saw Aang on the back of Roku's Dragon...I do not know if there was originally a thread about this... Since Iroh had journeyed to the Spirit World is this the reason? I doubt that this will be covered by the end of the series i am just interested in other thoughts and opinions on this matter also