One possible plot could be that Astrid is cursed by an evil sorcerer. At first, she has no idea what's happening to her but slowly starts to notice physical changes like her skin getting scaly. As she turns more and more into a dragon, she has to struggle to maintain her relationships with her friends who are initially afraid of her new form. Eventually, she discovers a way to break the curse through an ancient magic ritual.
Maybe Astrid accidentally enters a forbidden magical area. There, she comes in contact with a powerful dragon - themed magic that starts to transform her. In her dragon form, she finds that she has new abilities like flying and breathing fire. She then uses these powers to protect her village from a series of attacks by a neighboring warlord. Her friends gradually accept her new form as they see how she uses it for good.
The plot could be that Astrid is part of a magical experiment gone wrong. The experiment was aimed at creating a human - dragon hybrid for some noble purpose, but it backfires on Astrid. She turns into a dragon completely. She embarks on a journey to find the origin of the experiment in order to reverse it. Along the way, she meets other magical creatures who either help or hinder her progress.
In the fanfic, Astrid could be part of a scientific experiment gone wrong. The experiment was meant to study dragon DNA, but something malfunctioned and she starts to transform. She then embarks on a journey to find a cure. Along the way, she discovers that being a dragon gives her a unique perspective on the world and she has to decide if she really wants to go back to being fully human.
Perhaps an ancient dragon that has been sleeping for centuries and wakes up to find Astrid turning into a dragon. This dragon sees Astrid as an abomination because she was not born a dragon but is becoming one through some unnatural means. So, it decides to hunt her down and destroy her.
Perhaps a jealous wizard. He was once friends with Astrid but when he sees her gain the power and beauty of a dragon, he becomes envious. He starts to cast spells to make Astrid's life as a dragon difficult and tries to steal her new - found powers for himself.
One possible plot could be that Eragon, while facing a powerful dark enemy, discovers a hidden ancient magic that causes him to transform into a dragon. As a dragon, he has to quickly adapt to his new form, learning to fly and use his newfound dragon abilities like enhanced strength and fire - breathing. He then uses these powers to defeat the enemy and protect his land.
One possible plot could be that Issei discovers a hidden power within himself that gradually transforms him into a dragon. This new form gives him enhanced strength and abilities, but also attracts the attention of powerful enemies who want to either control him or eliminate him. He has to learn to master his dragon form while also protecting his friends and loved ones.
One possible plot is that Astrid is on a quest and she encounters a dragon. The dragon licks her as a form of greeting or acceptance. This lick then forms a bond between them, and they go on adventures together. The fanfic could explore how their relationship develops, with the dragon's lick being a central and unique aspect of their connection. It might also involve Astrid learning more about the dragon's world and the significance of the lick within it.
The purpose or the mission that Astrid has as a dragon is often a central element. Maybe she has to save the dragon world from a threat, or she's on a quest to find out more about her new form and its origin. This gives direction to the fanfiction story.
One possible plot could be that Harry is under a powerful dark spell. The transformation into a dragon might be a part of a scheme by Voldemort or his followers to either discredit Harry or use his new form for some evil purpose. Maybe Harry has to learn to control his dragon form in order to fight back and protect Hogwarts and his friends.
Maybe in the fanfiction, Natsu's emotional state causes him to turn into a dragon. After a great loss or a fit of extreme rage, his magic reacts and he transforms. This new form is both a blessing and a curse. It gives him the power to protect his loved ones better but also isolates him as he struggles to understand and control his new dragon instincts.
One possible plot could be that Hiccup's transformation into a baby dragon is the result of a magic spell gone wrong. He then has to figure out how to reverse it while experiencing the world from a dragon's perspective. He might make new dragon friends who help him understand his new form and search for a cure.