Avatar: The Last Airbender is indeed an original story. It has its own distinct style and narrative that sets it apart. The combination of elements like bending powers, diverse characters, and complex story arcs make it a one-of-a-kind creation.
Definitely not real. It's a fantasy world crafted with unique characters and magical elements that exist only in the realm of imagination and storytelling.
One idea could be a crossover with the Harry Potter universe. The Avatar characters could attend Hogwarts and learn magic while also using their bending abilities. For example, Aang could use his airbending to enhance his flying on a broomstick. Another idea is a crossover with the Star Wars galaxy. The benders could be like Jedis, using the Force which is somewhat similar to bending the elements. They could help the Rebels in their fight against the Empire.