One interesting plot twist could be that the boy and girl seem to get along great at first, but then they find out they are from rival families. For example, their families own competing businesses in town. Another could be that the girl has a secret identity. Maybe she's a famous singer in disguise and the boy discovers this later. It could also be that the boy meets the girl thinking she's single, but then finds out she's engaged to someone else, but she's not really in love with her fiancé.
A plot twist could be that the boy and girl meet in a dream - like situation. They have a wonderful encounter, but when they wake up, they are in different time periods or even different dimensions. Or perhaps the boy meets the girl, and she seems perfect. But as they start to get closer, the boy realizes that the girl has a twin sister, and he's been mixing them up all along. Also, it could be that the boy meets the girl at a masquerade ball, and they fall in love without seeing each other's faces. Later, when they see each other without masks, they are shocked by the appearance but still feel the connection.
One common plot twist is that they initially dislike each other but then fall in love. For example, in some stories, the boy and girl might have a bad first encounter, like getting into an argument over a misunderstanding. But as they get to know each other better, they realize they have a lot in common and start to develop feelings.
A plot twist might be that just when they are about to get together, an old flame of either the boy or the girl shows up. Say the boy's ex - girlfriend suddenly comes back into town and tries to win him back, creating drama and uncertainty in the budding relationship.
One idea could be a crossover where characters from both shows meet in a shared universe. For example, Cory and Topanga from 'Boy Meets World' could meet Riley and Maya from 'Girl Meets World' and they all go on an adventure together in New York City. They could help each other with their personal and relationship problems, sharing their different experiences from their respective shows.
Well, perhaps the merman has a twin brother who is evil. When the tumblr boy meets the merman, the evil twin starts to cause trouble. He tries to make the tumblr boy and the merman fight against each other. Or it could be that the merman's home, the underwater world, is in danger of being destroyed by a powerful force from the land. And the tumblr boy has to choose between helping his own kind or saving the merman and his world.
One interesting plot twist could be that Naruto discovers he has a long - lost older sibling who was thought to be dead. This sibling could be a powerful ninja with a different view on the Hidden Leaf Village, causing Naruto to question his own beliefs. Another twist could be that the Nine - Tailed Fox has a secret ability that no one knew about, which Naruto has to master in order to defeat a new, extremely powerful enemy.
A plot twist could be that Hotaru is secretly related to the main villain. This would put her in a difficult position as she has to choose between her loyalty to Utakata and her new - found family connection. It would also add a layer of complexity to her character.
A possible plot twist could be that Astrid discovers she has some special powers during her pregnancy that are related to the dragons. This could change the way they view the pregnancy and the future of their child. Another twist could be that Hiccup is told he has to go on a very dangerous mission right when Astrid is in a critical stage of pregnancy.
One interesting plot twist could be that Naruto has hidden powers that are only awakened when he discovers his true heritage as Kaguya's son. These powers could be something completely different from what he already has, like the ability to control space - time in a unique way.
Time - related twists. For example, one of the characters discovers they can time - travel and they accidentally change something in the past that affects their relationship in the present. Or, they find out that their relationship was predestined through some time - bending prophecy.
A boy, Jack, was in a coffee shop. He was waiting for his friend. A girl, Emma, entered the shop. She was looking for a place to sit. There were no empty tables, except the one where Jack was. Jack noticed her dilemma and offered her a seat. They began chatting casually. Jack found Emma's stories about her travels fascinating. Emma liked Jack's sense of humor. By the time Jack's friend arrived, Jack was more interested in getting to know Emma better. So he asked her out for dinner the next day.