The Air Nomads have many parallels to real-world Buddhist monks, including the way in which they discover a reincarnated leader. The method of hiding artifacts from past lives amidst mundane items and observing whether a prospective child Avatar correctly chooses the artifacts is based on one of the many tests used to discover the reincarnated Dalai Lama.
This is the first time Uncle Iroh redirects lightning.
In The Art of the Animated Series, it states that the Fire Lord's war room is inspired by Chinese and Egyptian architecture.