A crossover with 'The Magic School Bus' might be cool. Ms. Frizzle and her class could shrink down and enter a human body where they meet Osmosis Jones. Together, they could learn about the immune system and help Jones fight off a particularly tough germ. The students could use their scientific knowledge from school to assist in the battle.
Another possibility is a crossover with 'Men in Black'. Osmosis Jones could be recruited by the Men in Black to deal with alien viruses that are invading human bodies. He would have to adapt his skills to deal with extraterrestrial threats while also learning about the Men in Black's technology and methods of dealing with alien threats.
Some Osmosis Jones fanfiction ideas might involve relationships. For instance, a story about Osmosis Jones falling in love with another cell in the body. It could be a comical love story where they face challenges like misunderstandings and the chaos of the body's functions. Or, there could be a fanfiction where Osmosis Jones has to mentor a young, inexperienced cell and teach it the ropes of protecting the body. Also, a story about Osmosis Jones getting lost in a maze - like part of the body and having to find his way back while fending off germs would be interesting.
One idea could be Osmosis Jones having to team up with a new type of cell that has a unique ability, like a cell that can time - travel within the body. They have to go back in time to stop a virus from mutating into a more dangerous form that it will become in the future.
You could write an OC fanfiction where the OC is a foreign cell that enters Frank's body. This cell has different rules and functions compared to the native cells. It initially causes chaos as the body's systems don't understand it, but Osmosis Jones realizes its potential and tries to work with it to fight off a super - virus that is immune to the normal defenses. The OC could bring in new ways of fighting diseases from the outside world it came from.
A crossover with Iron Man could be really cool. Imagine Tony Stark recruiting Jessica Jones for a special mission. Jessica's no - nonsense attitude might clash with Stark's ego at first, but they could end up making a great team and saving the day in a very different way than either is used to.
The Incredibles could be great characters to include. They have superpowers, and in a crossover, they could use their powers to help Osmosis Jones in his fight against a super - strong virus. For example, Mr. Incredible could use his strength to physically remove large clumps of the virus, while Elastigirl could stretch into small areas to reach hidden viruses.
One idea could be that Jessica and Daredevil team up to take on a powerful criminal organization that has been causing chaos in Hell's Kitchen. Their different skills - Jessica's super strength and Daredevil's enhanced senses - would make for an exciting combination as they fight through the seedy underbelly of the city.
Maybe a common enemy from their past resurfaces. This enemy has a vendetta against both of them and is using their knowledge of Daredevil and Jessica Jones' weaknesses to try and take them down. They have to put aside their differences and figure out a way to stop this person before it's too late. For example, the enemy could be a former associate from one of Jessica's PI cases who also has a connection to Daredevil's world of crime - fighting in Hell's Kitchen.
One idea could be that the OC is a new cell in the body and accidentally stumbles upon Thrax while he's on one of his evil missions. Thrax is initially intrigued by this unknown entity and decides to toy with the OC instead of attacking right away.
A more complex plot could be Bridget Jones discovering during her pregnancy that there are some family secrets that could potentially affect her unborn child. She then embarks on a journey to uncover these secrets while also dealing with the physical and emotional changes of pregnancy. This could involve meeting long - lost relatives or finding out about a family curse or blessing that she had no idea about before.
Perhaps Hestia Jones and Harry team up to rescue some captured magical creatures. They could face many obstacles along the way, and in the process, develop a strong bond of friendship.