Mowgli himself is often a great character in mowgli fanfic. His ability to communicate with animals and his unique upbringing make him full of potential for different storylines.
There might be a mowgli fanfic where Mowgli tries to bring peace between two rival animal groups. He uses his knowledge of both sides to negotiate and find common ground. This could involve a lot of drama and tense moments as the two sides are initially very hostile towards each other.
Well, obviously the main characters are Kaa and Mowgli. Kaa is the sly and intelligent snake, known for his hypnotic powers. Mowgli is the man - cub, who is trying to find his place in the jungle. Their interactions form the core of the fanfic.
Perhaps an ancient evil spirit that has been awakened by the mixing of the two worlds - Ariel's underwater world and Mowgli's jungle world. This spirit wants to plunge both worlds into darkness. It starts by causing natural disasters in both areas, like huge storms in the ocean and forest fires in the jungle. Ariel and Mowgli must figure out a way to stop this spirit before it's too late, by finding ancient artifacts that can seal the spirit away again.
One possible plot could be that Ariel, being curious about the jungle, somehow ends up in Mowgli's world. Mowgli could show her around, introducing her to his animal friends like Baloo and Bagheera. Ariel might be amazed by the different kinds of land animals and plants she has never seen before. And in return, she could tell Mowgli about her underwater world, with all the colorful fish, the mermaid kingdom and the adventures she had there. Their friendship could develop as they learn from each other's different cultures and ways of life.
In the Jungle Book Mowgli story, Mowgli's main adventures include his struggle against the evil Shere Khan. Shere Khan wants to kill Mowgli because he is a human. Mowgli, with the help of his animal friends, tries to outwit the tiger. He also has adventures in learning the jungle's secrets. He learns how to climb trees like a monkey, swim like a fish in the jungle rivers, and hunt small prey. His relationships with the other jungle animals, whether friendly like with Bagheera and Baloo or hostile like with Shere Khan, form the core of his adventures.