How about a fierce Growlithe? The Growlithe could initially see the miltank as a rival for the male human's attention. But as the story progresses, they all find themselves in a situation where they have to work together to save a group of baby Pokémon. This forces the Growlithe to put aside its differences and team up with the miltank and the male human, creating a more diverse and interesting dynamic in the fanfic.
Perhaps in the fanfic, the male human is a trainer who has a special connection with his miltank. They enter a Pokémon competition together where they face tough opponents. The miltank's unique moves and the human's strategic thinking make them a formidable team. Along the way, they also have to overcome some misunderstandings within the Pokémon community about their unusual partnership.
One common theme is friendship. The male reader often forms a strong bond of friendship with the miltank, which is central to the story. For example, they might rely on each other during difficult times.
One idea could be the symbiote giving the human male some extraordinary powers, like enhanced strength and agility. The male then has to learn to control these new abilities while hiding them from the world. Another plot could involve the symbiote having a mind of its own and conflicting with the male's moral code. For example, the symbiote might want to take revenge on someone who wronged it in the past, but the male is against violence.
A young detective who idolizes Batman from afar and tries to help him in secret. This character could bring a fresh perspective to the story and also add some mystery as Batman tries to figure out who this helpful stranger is.
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.
One idea could be a story where a human scientist is studying sharks and forms an unexpected bond with a particularly intelligent shark. They communicate in some unique way and end up helping each other, like the shark leading the human to a hidden underwater treasure which in turn helps the human protect the shark's habitat.
The 'pinkamena x human fanfic' might also be interesting in terms of character development. Pinkamena's unique personality traits could be further explored in relation to a human character. Maybe it shows how she adapts to the presence of a human or vice versa, which can create a lot of engaging storylines.
A 'human x noivern fanfic' could be about a human who has the ability to communicate telepathically with Noivern. They team up to stop an evil force that is threatening the Noivern's natural habitat. Along the way, they learn about each other's cultures and the human gains a new perspective on the world of Pokémon, specifically the Noivern species.
One interesting concept could be the exploration of transformation. Since a chrysalis is associated with metamorphosis, in the fanfic it might symbolize a character's personal growth or change. For example, the human character could learn valuable life lessons from their interactions with the chrysalis - like patience, as they wait for the transformation to occur.
One idea could be a story where a human trainer has a special bond with a Pikachu that allows them to communicate telepathically. Another could be a human getting lost in the Pokemon world and having to team up with various Pokemon to find their way back home. Or perhaps a story about a human who discovers they have the power to transform into a Pokemon.