One popular theme is Dean's struggle to recover from the car accident, both physically and mentally. It could involve him dealing with injuries and the fear of not being able to hunt again. Another theme might be how the other characters, like Sam, react to Dean's accident and support him through the tough times.
In Supernatural fanfiction, Dean often has different relationships. His girlfriends can range from original characters created by the fanfic authors to characters from the show's universe in alternate scenarios. For example, some fanfictions might pair him with a hunter from another part of the world, adding new dynamics to his character as he navigates a relationship while still dealing with hunting demons and monsters.
Some start with the aftermath of the accident. They show Sam or other characters finding Dean in the wrecked car, his injuries, and the immediate panic and worry that follows. This way, the readers are immediately drawn into the emotional turmoil of the situation.
Dean would probably be extremely confused at first. He might stand there, staring at his car with a bewildered look on his face, muttering things like 'This can't be real'.
His complex personality. He can be tough as nails on the outside, but he has a soft heart. Fanfiction writers love to explore this contrast, showing his vulnerability when he's alone or dealing with personal issues.
Often, his relationships with other characters change. His bond with Sam might be affected as he gets closer to the angels. He might also make new friends or enemies among the angelic ranks, which forces him to grow and adapt in different ways than he did as just a hunter.
In fanfiction, when Dean becomes a Prince of Hell, his personality could shift. He may start to see things from a more demonic perspective. His relationships with other characters would be redefined. For example, his bond with his brother Sam could be strained as Sam tries to save Dean from his new, dark self.
Tickling in the context of Dean and witches in Supernatural fanfiction might also be a way to humanize the witches. Instead of always being the 'bad guys', they could be shown as having a sense of humor or playfulness through this tickling scenario. And for Dean, it's a new and strange experience that challenges his usual understanding of the supernatural world.
Well, in some fanfictions, Dean as a Knight of Hell has enhanced physical abilities. He can be faster, stronger, and more resilient. This makes him a formidable force in battles against both demons and other supernatural creatures.
A clothed and gagged Dean in Supernatural fanfiction could be a result of a spell. Some dark magic user might have put a spell on him to keep him from speaking incantations or warnings. This would lead to an interesting plot where the other characters have to find a way to break the spell and free Dean.