Well, perhaps in the fanfiction, Batgirl is on a mission in her own world and stumbles upon a strange portal that transports her to the Hidden Leaf Village in the Naruto world. There, she meets Naruto, who is intrigued by her unique gadgets and fighting style. They start training together, with Batgirl teaching Naruto some of her stealth and hand - to - hand combat techniques, and Naruto showing her how to use chakra in return. Eventually, they face a powerful new threat that requires both their sets of skills to defeat.
The plot might center around a mystery that ties to both Young Justice's world and Batgirl's. For instance, some sort of ancient artifact that has the power to disrupt both the meta - human world and Gotham's criminal underworld. Young Justice brings their diverse powers and abilities, while Batgirl offers her detective skills and knowledge of Gotham. As they search for the artifact, they face various challenges and enemies.
Well, it might involve Batgirl initially being a bit of an outsider among the Justice League. But then she proves her worth by taking on a powerful villain that the League has trouble with. For example, she could use her agility and stealth to infiltrate the villain's lair and gather crucial intel that the League needs to make their big move.
One possible plot could be a training session. Team 7, consisting of Naruto, Sasuke, Sakura and Kakashi, might meet Team Minato, which includes Minato, Obito, Rin and Kakashi in his younger days. They could engage in friendly sparring matches. Naruto would be excited to meet his father Minato and learn some new jutsu from him. The two teams could also exchange stories about their adventures, like Team 7 talking about their battles against the Akatsuki, and Team Minato sharing their experiences during the Third Great Ninja War.
In this fanfiction, there could be an epic battle of skills. Team Minato, with their unique abilities from their time, could test the mettle of Team 7. Maybe Minato's lightning - fast speed would be pitted against Naruto's new - found powers. It would be a clash of different generations of shinobi.
The League of Shadows could be a great antagonist. They might see Young Justice as a threat to their plans in the world and Batgirl as an obstacle in Gotham. They could try to manipulate situations to make Young Justice and Batgirl turn against each other while they carry out their own devious plans, like releasing a dangerous virus in a major city.
The Court of Owls would be a great main villain. They are a powerful and secretive organization in Gotham. Their connection to Gotham's history and their shadowy nature could pose a huge threat to both Young Justice and Batgirl. They might be after some meta - human power or trying to take over Gotham in a new way.
It could be the Joker. Since he's one of Batgirl's main foes in Gotham, his chaotic nature would pose a great threat to the Justice League as well when they enter Gotham's affairs.