Crookshanks has a very special relationship with Hermione. In fanfiction, it's often shown as a deep bond of loyalty. Hermione trusts Crookshanks completely, and he, in turn, is always by her side, protecting her in his own cat - like ways. For instance, he might hiss at any potential danger that approaches Hermione.
He might have some magical abilities that are not fully known yet. Maybe he can create a sort of magical distraction. In a battle, Crookshanks could start making strange magical noises or auras that disorient the enemy. Since he is a very intelligent cat, he could also be able to analyze the battle situation and lead some of the smaller magical creatures like house - elves to attack the weak points of the enemy's formation.
One plot idea could be that Crookshanks discovers a hidden passage in Hogwarts that leads to an ancient wizarding library. He then leads Hermione to it, and they find a powerful spellbook that helps them in their fight against the dark forces. Another could be that Crookshanks has a secret ability to communicate with other magical creatures in the Forbidden Forest and he enlists their help to save Harry from a dangerous situation. Maybe he can talk to the centaurs and they come to the rescue when Harry is surrounded by Death Eaters.
Crookshanks in the 'Harry and Crookshanks' lemon fanfiction could be important for several reasons. First, it might be used to add a touch of the familiar from the original Harry Potter series into this fan - created world. Second, it could play a role in the emotional development of the story. For instance, if Harry has a strong bond with Crookshanks, it can affect how he behaves in the 'lemon' parts of the fanfiction. Also, Crookshanks might be a source of humor or light - heartedness in a story that could potentially have some more intense or adult - like themes. This can create a balance and make the fanfiction more engaging.
A more comical storyline could be Crookshanks accidentally getting into a magical mishap that gives him the ability to talk for a day. He then spends the day criticizing Ron's treatment of him, while also sharing some of the secrets he's learned from prowling around the Gryffindor common room at night. Hermione is both amused and exasperated as she tries to keep Crookshanks out of trouble.
The 'Harry and Crookshanks' lemon fanfiction likely deviates from the original series in terms of the nature of the relationship. In the original, the relationship between Harry and Crookshanks was more of a normal pet - owner type. But in the fanfiction, especially with the 'lemon' aspect, it might involve more complex and perhaps inappropriate relationships. Also, the plot might take wilder turns as it's not bound by the original story's constraints.
Obviously, Crookshanks is a main character as it is the Potter's cat in this fanfiction. The Potter family members would also be main characters. Harry Potter himself would likely be important as he is the central figure in the Potter family. His friends might also make appearances as they often visit the Potter home, and their interactions with Crookshanks could be part of the story.
Well, it could be that Crookshanks, as the Potter's cat, has a special bond with the Potter family members. It might have some unique magical abilities that are explored in the fanfiction. For example, it could be able to communicate with the Potters in a special way, or perhaps it has a connection to the magical defenses of the Potter household that we don't know about in the original series.
You can start by looking on fanfic platforms like Archive of Our Own (AO3). It has a large collection of Harry Potter - related fanfics, including many focused on Hermione and Crookshanks. Fanfiction.net is also a good place to search. There are likely to be some great stories about them there as well.
Well, just based on that title alone, it's difficult to determine its quality. There are so many aspects that make a Harry Potter fanfic great. For example, it could explore new relationships between the characters, or create exciting new magical adventures. But we don't know if 'skull is harry potter fanfic' does any of those things. So, it might be good, it might not.