I dont know if any one has brought this up
I was just watching the 2 min clip of the season finale, I was watching zukos new attitude.
then I noticed how much Iroh new of Zukos illness.
so my thinking is that Iroh possibly went thru this after the death of??his son??and ending his seige of Ba sing sa.
this might be the way normal (benders) people enter the spirit world.
what do you guys think?