One common theme could be mystery. Since 'light gets caught' might imply something unexpected or strange happening with light, it could lead to a mystery - like what caused the light to be caught and what are the consequences. Another theme might be transformation. The event of the light getting caught could potentially change a character or a situation in some way.
Well, in 'light gets caught' fanfiction, a possible theme is discovery. The characters might discover something new about their world or themselves as a result of the light getting caught. Also, a theme of power struggle could exist. If the light has some sort of significance or power, different characters might fight over it or try to control it once it's caught.
I haven't come across much 'light gets caught' fanfiction myself. But you might want to check out relevant fan communities on social media platforms. They often share and discuss interesting fanfics in this area. Maybe someone there can point you to some great ones.
In some fanfictions, Dumbledore is portrayed as having a lot of secrets. If he gets caught, it could be related to his past. Maybe some old enemies find out where he is and catch him. Then he would have to deal with his past coming back to haunt him. His friends might try to rescue him, but it would be a very difficult situation for him, and it could change the whole dynamic of the fanfiction story.
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.
Since I haven't actually read this particular fanfiction, it's hard to say for certain. However, based on the title, we can assume that Richie is the main focus. The Deadlights are likely some sort of supernatural or dangerous element. It could involve Richie being trapped in a world created by the Deadlights, facing his worst nightmares perhaps, and the story might be about his journey to break free from this terrifying situation, whether through his own strength or with the help of others.
One common theme is family relationships. Since 'One Day at a Time' focuses a lot on family, fanfictions often explore different aspects of the family dynamic, like how the characters support or clash with each other. Another theme could be the characters' personal growth and how they overcome challenges in their lives, just like in the original show.
One common theme is justice. Naruto seeking revenge is often seen as a way to right the wrongs done to him or his loved ones. It's about making the guilty pay for their actions.
Betrayal is a common theme. Usually, something or someone has wronged Harry deeply, which sets him on the path of revenge. For example, it could be the Ministry of Magic turning against him or a supposed friend revealing his secrets.
One common theme is trust. When Sonic is betrayed, it shatters the trust he had in his friends or allies. This often leads to a journey of rebuilding that trust or finding new trustworthy companions.
One common theme is self - discovery. When Anna gets powers, she often has to figure out what she can do with them and how they fit into her identity.
One common theme is friendship. When Mario gets sick, his friends always come to his aid, showing the strong bonds between them.