There could be a jealous noble in the little king's court. This noble, seeing the little king's interest in the princess and the bouquet, decides to create trouble. He might spread false rumors about the princess or try to steal the bouquet to make the little king look bad in front of his people.
Maybe a dragon. Dragons are often depicted as villains in stories. The dragon could have its lair near the princess's castle and be attracted to the magical bouquet. It would constantly threaten the princess and the little king, trying to steal the bouquet for itself.
It could be an evil sorcerer. The sorcerer might want the princess's bouquet for its magical powers. He could be jealous of the little king's growing influence and try to stop him from getting close to the princess and the bouquet.
It could be that the princess's bouquet is the key to a hidden treasure. The little king, being a shrewd and brave leader, wants to find this treasure for the betterment of his people. He approaches the princess, who is guarded by magical creatures. The story then unfolds as the little king tries to convince the princess to let him use the bouquet to find the treasure, and in the process, they learn about each other's values and dreams.
It could be an evil Digimon that has the power to control other Digimon and wants to use them to invade the Naruto world. This Digimon might be jealous of the Digimon King's power and Naruto's connection to it, so it aims to destroy both of them. It could have abilities like mind - control and dark energy attacks.
The Penguin could be a great main villain. He could be up to his usual schemes in Gotham, like stealing valuable artifacts. When the little boy witnesses one of his crimes, the Penguin tries to silence him. Batgirl then has to protect the boy and stop the Penguin's evil plans.
In a reverse little mermaid story, the mermaid herself could be the villain. Instead of being the kind - hearted character we know, she could be cruel and use her charm to manipulate humans for her own gain.
Ursula is an obvious choice as she is the main villain in the original Little Mermaid story. In a Kingdom Hearts fanfiction, she could be even more powerful, perhaps having made a deal with the Heartless or some other dark force to gain more control over the underwater world and other worlds connected to it.
A jealous witch who was the one who originally cast the curse on the Beast could be the main villain. She might see the little sister's presence as a threat to her plan of keeping the Beast trapped forever. Maybe she tries to trick the little sister into making things worse for the Beast.
Maybe a new character, a powerful sea witch who has been influenced by the power - hungry ways of some of Naruto's villains. She wants to rule both the underwater world and the land world above. She would use her magic to create chaos and try to stop Naruto and Ariel from uniting their forces.
The main characters are obviously the princess and the king.
The main characters are the king, who represents power and authority in the story, and the princess, who might be a symbol of beauty and grace. There could also be other secondary characters like the king's advisers or the princess's servants, but the king and the princess are at the heart of the story.
The main character is surely the little princess herself. There might also be her parents, like the king and queen. And perhaps a loyal servant or a best friend who accompanies her on her adventures.