Thank you for the facts Imgur user pbpills!
1. Aang was 12 when he was frozen for 100 years, making him 112 at the beginning of the series.
2. a) Waterbending is based off of the martial art fighting style Tai Chi.
b) Airbending is based off of the martial art fighting style called Ba Gua Kung Fu.
c) Earthbending is based off of the martial art fighting style Hung Car.
c-2) Toph has her own unique Earthbending style mased off of the martial art fighting style Southern Praying Mantis.
d) Firebending is based off of the martial art fighting style Northern Shaolin Kung Fu.
3. The first and second episodes of Avatar: The Last Airbender were originally written as a one-hour event
4. The voice actor of Tahno, Rami Malek, was cast as Benjamin for the second part of Twilight Saga's: Breaking Dawn.
Benjamin is a vampire with the ability to manipulate the four elements; much like the Avatar.
5. The first time Azula showed signs of firebending was when Zuko stole her favorite toy...
... she reacted by lighting his ponytail on fire.
6. Momo was supposed to be the reincarnation of Monk Gyatso.
7. Zuko gets a scar on his lower chest, in the exact same place as the one on Aang's back.
8. The BOULDER has a tattoo of a badgermole on his back.
I can't find the picture, but it's there, trust me.
9. In the Dutch dubbed version of Avatar: The Last Airbender, Toph calls Aang "Ballerina" instead of "Twinkle Toes".
10. An airbender's sneeze can create more propulsion than a modern day jet engine.
11. The War between the Equalists and non-benders is parallel to the 1900's war between the Communists and Nationalists.
12. The Earth Kingdom is ran like the Holy Roman Empire...
.... with several small kingdoms serving under one overarching rule.
13. Zuko only laughs twice throughout the series.
14. Sokka fishes with a traditional whale tooth saber.
15. Katara is the first person in the series to touch Zuko's scar.
Mai is the second, other than Zuko himself.
16. The voice actor of Commander Zhao is also the actor who plays Lucius Malfoy in the Harry Potter Films.
17. The voice actor of Older Aang also voices Sitka from Brother Bear...
...both of whom are heavily spiritual characters.
18. The Brazilian Synchronized Swimming Team used Avatar: The Last Airbender's theme song...
...for their performance at the London 2012 Olympics.
19. In Hinduism, the second chakra is located near the sexual reproductive organs.
Because it is related to pleasure, the location of this chakra was left out of any dialogue.
20. Katara has been in every season Finale of Avatar, including Legend of Korra.