One plot idea could be that they face challenges in preparing for the arrival of their baby. Maybe they have to deal with threats from villains in the Sonic universe who see their unborn child as a potential weapon or a way to manipulate them.
Another plot could revolve around the reactions of their friends. For example, Sonic and the others might be initially shocked but then become very supportive. They could help Tails and Cosmo build a safe place for the baby. And there could be a lot of heart - warming moments as they all come together for this new life. The fanfiction could also explore how Tails and Cosmo's relationship grows even stronger during this time.
Maybe Cosmo was turned into a different form, like a small, helpless creature. Tails stumbles upon her in this state while on a routine exploration. At first, he doesn't recognize her, but as he gets closer, he realizes it's Cosmo. He then devotes all his time to finding a way to turn her back to her normal self. Along the way, they form a deeper bond, and when she finally returns to her original form, it's a beautiful reunion.
Another plot could involve the daughter going on a journey to learn more about her parents' past. Along the way, she meets different characters who knew Tails and Cosmo. This journey of self - discovery also helps her to understand her own place in the world and her unique abilities.
One idea could be that Cosmo and Tails work together to build a new type of spaceship. They use their combined knowledge of mechanics and botany. Cosmo might contribute with her understanding of plant - based energy sources, while Tails uses his engineering skills. Another plot could involve them exploring a mysterious new planet where they encounter strange creatures. Cosmo could communicate with the planet's plant - like life forms, and Tails would figure out how to navigate the terrain.
Perhaps Tails and Cosmo's baby is born with some unique abilities. It could inherit Tails' intelligence and mechanical aptitude along with Cosmo's connection to nature. They face challenges in protecting their baby from those who might want to use its powers for bad. So they go on an adventure to find a place where they can raise the baby in peace.
One challenge could be different species differences. Since Tails is a fox - like creature and Cosmo is more of a plant - based being, they might have different life expectancies or biological needs. For example, Cosmo might need more sunlight than Tails. Another challenge could be the acceptance of their relationship by others. Some of their more traditional friends or family members might not understand their union at first.
One approach could be to start from the general relationship between Tails and Cosmo in the Sonic universe. Since their relationship was quite touching in the original story. Writers who are interested in exploring their story further might have created some pregnancy - related fanfictions. But it could be a relatively niche topic. You may need to dig a bit deeper by exploring different fan - created content related to Sonic and its characters.
One challenge could be the difference in their species. Tails is a fox - like creature and Cosmo is plant - based. Their different biological needs and life cycles might pose difficulties. For example, Cosmo might need more sunlight and water than Tails. Another challenge could be the acceptance of their relationship by their respective communities. Some might not understand or approve of their inter - species love.
One common theme is sacrifice. Since Cosmo has a selfless nature in the original story, fanfictions often explore her willingness to sacrifice for the greater good or for Tails. Growth and self - discovery are also themes. Tails, being a young and intelligent character, often goes through experiences in fanfictions that help him understand himself and his place in the world better. This is sometimes related to his relationship with Cosmo, as she can be a catalyst for his growth.
One common theme is friendship. Tails and Cosmo are often depicted as having a very strong bond. Another theme is adventure, as they are usually involved in some exciting exploration or mission.
Another theme is growth. Both characters develop throughout the fanfictions. Tails might become more confident in his abilities outside of just technology, and Cosmo could learn more about the world around her and how to better control her powers. This growth is often a result of their experiences together and the challenges they face as a duo.