One possibility is that Dumbledore gets caught spying on a group of Death Eaters. This would put him in a very dangerous situation as the Death Eaters are extremely cruel and loyal to Voldemort. He might be tortured for information about the Order of the Phoenix. However, Dumbledore is very resourceful and would probably be able to hold his own against them for a while, giving his allies time to figure out a rescue plan.
There's also a chance that Dumbledore gets caught by a group of rogue magical creatures. For instance, if he was exploring an area that was supposed to be off - limits to wizards and the creatures there saw him as an intruder. They might not be as rational as wizards and could hold him captive without really understanding who he is.
In such a fanfiction, Dumbledore might face consequences for his actions. For example, his manipulative ways could be exposed. Maybe his secrets regarding Harry Potter's upbringing and the true purpose behind his actions could come to light, leading to a loss of his respected status among the wizarding community.
In some cases, when Dexter gets caught, the people who catch him might try to rehabilitate him. They could think that there's still some good in him and attempt to change his ways. However, Dexter might resist this change as his nature is deeply ingrained. This could lead to a power struggle between him and those who want to reform him, creating a lot of drama and tension in the fanfiction story.
Well, it could be that Ash gets caught in the Pokeball by accident. Once inside, he might start to understand the feelings of Pokemon when they are captured more deeply. He could try to figure out a way to escape, and in the process, learn some secrets about how Pokeballs work that he never knew before.
Even some of the Hogwarts professors or students could catch Dumbledore. Maybe a curious student stumbles upon Dumbledore in a restricted area where he's doing something strange. Or a professor who has a different view on how to run the school catches Dumbledore in the middle of an action that they think is wrong for the school's environment.
The fanfiction could focus on Dumbledore's backstory. Fans might write about his early years at Hogwarts as a student, his friendships, and how he developed into the great wizard he became. It could also include his interactions with other magical creatures in more depth than the original series, such as having secret meetings with centaurs or merpeople to gain wisdom.
One possible plot could be that Dumbledore is framed for a crime he didn't commit. Maybe there's a dark wizard who has managed to plant false evidence against him. For example, evidence that he was involved in some sort of dark magic plot. Another could be that the Ministry of Magic, fearing his power and influence, decides to arrest him on false pretenses to gain more control over Hogwarts. This could lead to a lot of chaos in the wizarding world as Dumbledore has many allies and supporters who would not stand for his unjust arrest.
Well, Harry would probably have a very different upbringing. He'd be surrounded by Dumbledore's wisdom all the time. He might learn magic at a much faster pace and gain deeper insights into the wizarding world's history and secrets right from the start. Dumbledore could also protect him more effectively from the dark forces, as he's one of the most powerful wizards. And Harry would grow up in an environment full of magic and knowledge, which would shape him into a different kind of wizard compared to the original story.
Well, it could be that Rumple discovers some past wrong Dumbledore did to him or his kind. Maybe Dumbledore once meddled in Rumple's magical affairs and now Rumple wants to make him pay. He could start by using his unique magic to create chaos in Hogwarts, like making the staircases go haywire or the portraits misbehave.
Well, perhaps in the fanfiction, Dumbledore is arrested because of his ties to a certain group that the Ministry has deemed as a threat. For example, he might have been secretly helping a group of werewolves or half - bloods who are fighting for equal rights, and the prejudiced Ministry decides to arrest him to stop what they see as a subversive movement. This could lead to a great uprising within the wizarding community, with students and other professors trying to prove his innocence.