One idea could be exploring how Cosmo's pregnancy affects his relationship with Wanda. Maybe he becomes overly protective or more sensitive. Another could be the chaos it causes in Fairy World, like how the other fairies react to the news.
One idea could be exploring how Timmy's mom's pregnancy affects the family dynamics. Maybe the fairies have to be extra careful with their magic around the pregnant mom. Another idea is that a new character in Dimmsdale gets pregnant and the fairies get involved in some comical ways to make sure everything goes well during the pregnancy.
One idea could be creating an OC who is a long - lost relative of Timmy. Maybe this relative has some unique magical abilities that are different from Cosmo and Wanda's. For example, they can manipulate time in a small way, like slowing it down for a short period to help Timmy study for a test.
One idea could be a story where Timmy's new baby sibling gets fairy godparents too. Maybe they have some really unique wishes that cause all sorts of wacky adventures in Dimmsdale. Another could be a fanfiction where the baby is actually a magical being in disguise and the fairies have to protect it from evil forces.
One idea could be a crossover with 'The Powerpuff Girls'. Timmy Turner could meet the Powerpuff Girls and they could team up to fight an evil villain that combines the magic of Fairy World with the chaos of Townsville. Maybe Mojo Jojo teams up with Vicky to cause trouble and the combined forces of Timmy's fairies and the Powerpuff Girls are needed to stop them.
Another plot idea is that Vicky from Fairly Odd Parents somehow gets some ghost - hunting equipment and decides to hunt Danny. Danny, thinking she's just another annoying human at first, soon realizes she's more of a threat than he thought. Meanwhile, Timmy has to try and stop Vicky without getting in Danny's way or revealing the existence of fairies.
One idea could be to create a fanfic where Timmy wishes for a time - traveling adventure with his fairies. He could go back to the days when his parents were kids and see how they were like then. Another idea is to have a story where Cosmo and Wanda accidentally switch powers with other magical creatures in Fairy World and Timmy has to help them get their powers back while dealing with the chaos it creates.
Timmy could also be a good choice. He is always in the middle of Cosmo and Wanda's adventures. His narration could add a touch of innocence and humor. He might be a bit clueless at times but that would make the story more interesting as he tries to understand what's going on with Cosmo.
One idea could be creating an OC who is a long - lost relative of Timmy. Maybe a cousin from a far - off magical land who comes to visit. This OC could bring new magical adventures and challenges for Timmy and his fairies. Another idea is an OC that is a new student at Timmy's school who has a secret power related to wishes. They could team up with Timmy to solve school - related problems in a magical way.
One interesting concept is alternate timelines. For example, what if Timmy had different fairy godparents? Another could be crossovers with other shows. It's really cool to see the characters from Fairly Odd Parents interact with characters from different universes.
Fanfiction about Vicky from 'Fairly Odd Parents' can be really creative. Some might focus on her backstory, like how she became so mean. Maybe she had a tough childhood that made her that way. Writers could explore her relationships with other characters in new ways, perhaps showing a side of her that we don't see in the show.