They are popular because Aang is such a beloved character. His death in a fanfic creates a lot of drama and allows for exploration of different characters' emotions. Fans like to see how the other characters would react and grow in the face of such a great loss.
Well, a common theme in fanfiction is their romantic adventures. Fanfic writers love to imagine Aang and Katara going on secret dates to beautiful, hidden places. These could be secluded islands or magical caves. Their relationship in fanfiction can also be a bit more complex than in the original series. There could be misunderstandings due to their different upbringings. Aang being the last Airbender with a more carefree nature at times, and Katara being a strong - willed Water Tribe girl.
One great Aang fanfic is 'Aang's New Adventure'. It takes place right after the end of the series. In this fanfic, Aang has to deal with some leftover Fire Nation rebels who don't want to accept the new peace. It's really exciting as it shows Aang using his bending skills in new and creative ways to bring about peace once again.
Since I'm not familiar with this particular graphic novel, it could cover a wide range of themes. It may revolve around the dentist as a central character, showing their work - life balance in the context of their home. There could be stories about the history of the house and how it became a dental practice. It might also depict the community around the house and how the dentist and the house are perceived by the neighbors. It could be a story full of human interest, with the dentist's house serving as the backdrop for all kinds of interactions, emotions, and events.
I'm not sure. It depends on various factors and how the story was presented. Sometimes stories are based on real events but might have some fictional elements added for entertainment.
One possible 'Avatar Aang death fanfic' could be about how his friends deal with the grief. For example, Katara might struggle with the loss of her love while also having to step up and be a stronger leader in the Water Tribe. Another could focus on how the world changes without Aang's presence to maintain balance. Maybe new benders emerge in unexpected ways to fill the void he left.
Not having read the graphic novel, it's pure speculation. The main characters could include the dentist, who is probably central to the story. There might be a nosy neighbor who is always curious about what goes on in the dentist's house. Also, if there are any apprentices or trainees in the dental practice, they could be main characters. Maybe there's a patient with a phobia of dentists who has a character arc throughout the story.
La Casa de Papel is completely fictional. The plot, characters, and situations were all crafted by the writers for entertainment purposes. There's no real-life basis for it.