Well, his brothers would probably go on a wild rescue mission. They'd search every nook and cranny of the city. Maybe they'd get some help from April and Casey too.
In this fanfiction, Mikey might gain new and unexpected powers. Maybe he could develop the ability to control certain elements like water or fire, which would add a whole new dynamic to his character and the story.
It could be Shredder. He's always been after the turtles.
It could be the Foot Clan. They've always been enemies of the Turtles, and kidnapping Mikey would be a way to get back at them or gain some advantage.
In a fanfiction, Mikey might get hurt during a mission to infiltrate a Kraang base. He could be detected by security systems and get zapped by some sort of electric defense mechanism. This would leave him weak and in pain. His brothers would need to carry him out of there and find a way to reverse the effects of the zap. They'd be desperate to get Mikey back to his normal, energetic self.
One possible plot twist could be that Mikey was kidnapped by an unexpected enemy, like a former ally who turned bad. Maybe it was someone he trusted, and this betrayal adds a layer of drama.
I'm not sure specifically as I haven't read this particular fanfiction. But it might be about Mikey from the Teenage Mutant Ninja Turtles getting some sort of skin condition like shellacne. It could involve his friends helping him deal with it, or his own journey in handling this new and unexpected situation.
He might gain new physical abilities, like enhanced strength or speed.
Well, in such a fanfiction, maybe the other Turtles would have to take on a more protective role. They'd need to figure out how to take care of baby Mikey, like feeding him pizza mush or something. And Splinter would probably be super strict about their babysitting skills.
Well, in the TMNT fanfiction, if Splinter gets a doctor, it could lead to some interesting plot developments. Maybe the doctor discovers something unique about Splinter's physiology that the turtles didn't know. For example, there could be a hidden strength or a potential weakness that might change how they protect him.
In a 'l gets kidnapped fanfiction', there could be a lot of drama. Maybe his friends would start a search mission right away. They might follow some small clues like a piece of cloth from his clothes left at the scene.