Watching Avatar again...

So I finally caved and bought all three seasons of Avatar on DVD because Avatar is the best show EVER!!! I am now watching it with some of my friends, who are watching it for the first time. However, since I've already seen all of these episodes, I am starting to notice a lot more little tidbits that I never noticed before. For example, they mentioned Ba Sing Se a lot in the first season. Also, in "The Warriors of Kyoshi", during the scene with Katara and Aang in the market, if you look behind Aang, you will see a man arguing with a pole; it goes back to him later and he is slumped over in defeat, as if the pole won the argument. Iroh actually channeled lightning during "The Storm", a full season before that technique was ever mentioned. Those are just a few things that I noticed and I was impressed that the writers thought so far ahead, which only made me love this show all the more. Have you noticed anything like that?