One interesting plotline could be the discovery of a long - hidden power within a main character. For example, Sam might find out he has a unique ability that was suppressed all this time, which changes the dynamic of his relationships with Dean and other characters in the story.
Maybe it involves the big reveal of a character's true identity. Like an ally they thought they knew turns out to be something else entirely, say an angel in disguise who has been manipulating events from the shadows. This would create a lot of conflict and new story directions.
Another possible plotline could be the revelation of a long - forgotten prophecy. The characters might discover that they are key players in a prophecy that was lost to time. This would force them to re - evaluate their actions and future plans, and also bring in new threats and allies as different factions react to this discovery.
One interesting plotline could be that Adrien and Marinette accidentally reveal their identities to each other in a moment of panic during an akuma attack. Maybe they're both trying to save the other and in the chaos, their masks slip, literally or figuratively.
There could also be Castiel, the angel. He often plays a significant role in fanfictions, especially when there are revelations about the supernatural world or the plans of Heaven.
One interesting plotline could be how Ladybug and Chat Noir finally reveal their identities to each other in a very unexpected and emotional moment. Maybe it happens during a battle where they are forced to trust each other completely.
Perhaps in a fanfiction, Spider - Man reveals his identity to Aunt May in a moment of desperation. He's been keeping it from her for so long, but when he's severely injured and she finds him in his suit, he has no choice but to tell her. This then changes their relationship dynamic as she now has to deal with the knowledge that her nephew is a superhero and all the danger that comes with it.
One common plotline is when Merlin reveals his true identity to Arthur in a moment of great danger. For example, when Camelot is under a powerful dark magic attack and Merlin has no choice but to use his magic openly to save everyone.
One possible plotline could be that Ladybug and Chat Noir's identities are revealed during a major battle against a powerful akuma. This causes chaos at first as the citizens of Paris are shocked, but then they quickly come together to support the heroes in a new way.
Well, in some Supernatural 13x17 fanfiction, there might be a plotline where a side character from that episode gets a more prominent role. For example, they could be the key to solving a mystery that was only hinted at in the actual episode. It could also be about how the events of 13x17 change the future trajectory of the characters' lives in ways that the show didn't explore.
Perhaps a plotline where an Anbu member is revealed to have a personal connection to a major villain in the Naruto universe. This could create a lot of internal conflict within the village as they try to figure out how to deal with this revelation. For example, if the Anbu member is related to Orochimaru and has been secretly feeding him information, it would be a huge shock.
A great plotline would be if Jessica came back as a sort of supernatural being herself. Maybe she was brought back by a powerful witch, but not fully human. This would create a whole new dynamic as Sam would have to deal with her new state. She could be on a quest to find out who brought her back and why, and in the process, she and Sam could rekindle their relationship in a very different way compared to before.
Some fanfictions might focus on the emotional aftermath for Sam and Dean. Maybe Sam is more affected by what happened than he let on in the actual episode, and the fanfiction could explore his inner turmoil. Also, there could be plotlines where other hunters get involved in the events that followed 'No Rest for the Wicked' and how their presence changes the dynamic between Sam and Dean.