Perhaps Aang meets Vegeta. Vegeta's pride and initial hostility would contrast with Aang's peaceful and friendly nature. They could end up in a battle where Aang tries to use his airbending to outmaneuver Vegeta's powerful energy blasts. This could lead to Vegeta having a new respect for the power of bending and a strange friendship could form.
Piccolo's regeneration ability could be used in combination with earthbending. Earthbenders could create structures around Piccolo while he's regenerating, protecting him from attacks. And in return, Piccolo could use his special attacks, like the Special Beam Cannon, to break through enemy defenses that the earthbenders couldn't handle on their own.
A 'Dark Naruto Avatar The Last Airbender Fanfic' has the potential to be a thrilling read. Picture Naruto being influenced by the power - hungry villains in the Avatar universe. His transformation into a darker version could bring about a war between the ninja world and the Avatar world. His Rasengan could be combined with some form of bending, creating unique and powerful attacks. The fanfic could also show how the values of the two worlds clash when Naruto goes dark, and how the heroes of both universes have to come together to stop him.
In some fanfics, like 'The Time - Bent Destiny', the twist is that the time traveler isn't a bender at all in their own time, but when they go back, they gain bending abilities. This completely changes the power dynamics and their role in the story. It's a really cool concept as they have to quickly learn how to use these new powers while also dealing with the time travel situation.
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.
One idea could be a crossover with 'Harry Potter'. The Avatar could visit Hogwarts and learn about magic there. Maybe Aang could teach the students about bending while learning about spells himself. Another idea is a crossover with 'Lord of the Rings'. The airbenders could fly over Middle - earth and help in the fight against Sauron. They could use their bending skills to create distractions or help in battles.
There's also Sokka and Suki's relationship. Suki was a strong and independent warrior from Kyoshi Island. Sokka was initially attracted to her strength and confidence. Their love story was fun and full of action. They had their ups and downs, like when Sokka was confused about his feelings, but in the end, they had a great relationship that showed two different yet complementary personalities coming together.
Inspiration for plots can come from exploring the unexplored corners of the Avatar world. There are many regions and sub - cultures that the show didn't fully cover. Your OC could be from one of these areas and have a plot related to their home's discovery or protection. Fan theories are also a great source. Some fans might have ideas about what could have happened after the show ended or in between seasons. You can use these theories as a basis for your OC's story. And don't forget about the characters' relationships. A love triangle or a friendship in jeopardy can be a great plot device.
One popular plot is a female version of Aang having to deal with the same challenges of mastering the elements but with a different perspective. For example, she might face more doubts from the male - dominated bending world about her abilities. Another plot could be her forming unique relationships with the other characters. Like, her friendship with Katara might be different as they could bond over their shared experiences as female benders in a tough world. Also, her romantic relationships could be explored in new ways, perhaps with Zuko, where their story would be different from the original due to her being female.
In some 'Pokemon DBZ Crossover Fanfiction', the idea of fusion is really creative. Instead of just fusing DBZ characters like in the original DBZ, they fuse Pokemon with DBZ characters. So you might have Goku fused with a Charizard, creating a being with both Goku's combat skills and Charizard's fire - breathing and flying abilities. Also, the idea of using Ki attacks in Pokemon battles is interesting. It adds a whole new dimension to the battles, like a Pikachu using a Kamehameha - like electric attack.
One common theme is the power exchange. For example, in many fanfictions, characters from Avatar The Last Airbender will learn ninjutsu from Naruto characters or vice versa. This allows for some really creative battle scenes and power - up moments.