Well, one possible plot could be that Twilight and Flash face many challenges in raising their baby. Maybe the baby has some unique abilities that draw unwanted attention. They have to protect it from various threats while also teaching it about their different worlds.
One possible plot could be that they have the baby in a very unexpected way. Maybe some sort of strange science experiment gone wrong (but in a good way) that results in a baby. Kim and Shego then have to figure out how to co - parent despite their differences. Kim would bring her sense of justice and heroism, while Shego would have her tough - as - nails attitude.
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.
Perhaps Hiccup is on a journey to explore new lands and stumbles upon Elsa's frozen kingdom. He helps Elsa overcome some of her fears about her powers that have resurfaced. In the process, they develop feelings for each other. Once Elsa becomes pregnant, they must deal with the cultural shock of their two very different worlds. Hiccup has to introduce Elsa to the Viking way of life, while Elsa tries to make Hiccup understand the elegance and traditions of her kingdom. They also have to figure out how their baby will inherit and control both dragon - related and ice - based powers.
A plot might involve Ash and Anabel dealing with the reactions of their friends and family to the new baby. Some might be overjoyed while others could be worried about how they'll manage. They could also have adventures where the baby's presence adds a new dynamic, like the baby being able to sense when a pokemon is in distress and leading them to help.
One possible plot could be that Bones discovers she is pregnant unexpectedly. Booth is initially overjoyed but then becomes overly protective. They face challenges at work as they try to keep the news under wraps for a while. And as Bones' pregnancy progresses, they start preparing for the baby's arrival, from decorating the nursery to arguing over baby names.
One possible plot could be that Fox and Krystal face challenges in raising their baby in a world full of danger. Maybe they have to protect their child from an old enemy who resurfaces, seeking revenge on Fox by targeting the new - born. They would then embark on a journey to keep their family safe while also teaching their baby the ways of survival.
Maybe the fanfiction could explore a magical accident that results in a baby - like entity being created between Twilight and Flash Sentry. They then have to figure out how to take care of this new being while also trying to reverse the magic if it's not meant to be. For example, they might seek the help of Princess Celestia to understand what happened.
A plot might involve them having the baby unexpectedly. They are still young and not fully prepared. Maka would be determined to be a great mother while Kid is initially a bit panicked about the lack of symmetry in their new family situation. However, with the support of their friends, they learn to adapt. The baby could grow up to be a bridge between different groups in their world, uniting them with its unique charm and powers.
Perhaps it's a story about their friendship being tested. Flash Sentry gets an important mission that takes him far away from Ponyville. Twilight Sparkle is worried about him and has to deal with her own insecurities. In the end, their friendship prevails as Flash Sentry returns safely and they realize how much they mean to each other.
One possible plotline could be that they meet in a strange, otherworldly situation. Maybe Flash, with his super speed, accidentally runs into the Twilight universe and meets the characters there. They fall in love over time and decide to get married, facing the challenges of their different worlds and abilities.