In fanfiction, Merlin growing a beard could signify a passage of time or a new phase in his life. It might be a symbol of his increasing wisdom or a mark of a more mature and powerful Merlin. Maybe he grows it during a period of isolation, where he has time to focus on himself and his magic, away from the chaos of Camelot.
The beard could change his appearance so much that his friends don't recognize him at first. This could lead to some comical misunderstandings in the fanfiction. For example, Gwaine might challenge him to a fight thinking he's an intruder, or Gaius might think he's a new wizard in town. As the story unfolds, they would then discover it's actually Merlin, and this could lead to a deeper exploration of how appearances can be deceiving.
Well, perhaps the story could be about Percy's journey of self - discovery as he grows a beard. Maybe he starts to look more mature and it changes the way people perceive him in the fanfiction world.
Fans of Percy in the original story would likely be interested. If they love the character, they'd be curious to see how this new aspect of him, the beard, changes his character arc.
Well, perhaps in this fanfiction, Harry grows a beard as a sign of his maturity and the many years of hardships he has endured since defeating Voldemort. Maybe he's living a more reclusive life, away from the spotlight of the wizarding world, and the beard is like a shield from all the attention he used to get. He could be devoting his time to research on ancient magic, and the beard just gives him that wise, old - wizard look.
In a more humorous take on the 'Merlin tied to a bed' fanfiction, it could be that Merlin has fallen ill and the overly - protective Gaius has tied him to the bed to make sure he rests. Merlin, being the active person he is, complains constantly. Arthur comes to visit and teases Merlin about finally being still for once. Meanwhile, Merlin tries to convince Arthur to let him loose, promising that he'll be fine. Eventually, Gaius relents and unties Merlin, who then immediately starts bustling around the room.
If Merlin died in the fanfiction, it could trigger a series of tragic events. The balance of power could tip, and the villains might seize the opportunity to attack. It could also bring out hidden strengths in the remaining characters as they try to cope with the loss.
One more idea is that Merlin is tied to the bed in a dream - like state created by an ancient magic. In this dream world, he is faced with his deepest fears and insecurities. His friends in the real world notice his strange behavior and try to wake him up. Merlin, while in the dream, has to find the source of the magic that is binding him and break free. Through his inner strength and the memories of his friends, he manages to do so and wakes up, having learned more about himself and his magic.
If Merlin is a Dark Lord in fanfiction, it could be an interesting exploration of the 'nature vs. nurture' concept. Maybe he turned dark because of the constant fear of being discovered and persecuted for his magic. His actions as a Dark Lord might include taking over Camelot or exacting revenge on those who wronged him in the past. It gives a whole new perspective on his character.