What are the possible reasons for Harry being Dumbledore's pet in fanfiction?

One reason could be for comical effect. It's quite funny to think of the powerful and feared Voldemort as a pet. Another reason might be to explore a different power dynamic. If Voldemort is a pet, Harry has a certain level of control over him, which is a complete reversal of their normal relationship in the original story.

One implication could be a change in Harry's agency. If he's seen as a pet, he might seem less in control of his own actions and more like a tool for Dumbledore's plans. Another is that it could alter the way other characters view Harry. They might see him as less of an independent hero and more of Dumbledore's follower.

One reason could be that Harry discovers Dumbledore has been withholding information about his parents. For example, if Dumbledore knew more about the events leading to their death but didn't tell Harry. Another reason might be that Dumbledore's lies were related to Harry's destiny. Maybe Dumbledore painted a false picture of what Harry was supposed to do in the fight against Voldemort, which made Harry feel deceived when he found out the truth.

One reason could be that Dumbledore had too many other responsibilities in the wizarding world. He was the headmaster of Hogwarts and was constantly involved in dealing with the threat of Voldemort on a larger scale. He might not have been able to give Harry the individual attention and care that a true guardian should provide.

One possible reason could be that Dumbledore wants Harry to have a more normal upbringing away from the spotlight of Hogwarts and his own influence. So he deliberately steps back from the role of guardian.

One reason could be a change in Dumbledore's personality. If he's depicted as being cold or distant in fanfiction, Harry, who knew him as a mentor figure, might not like it.

Perhaps there are safety concerns for the students that Dumbledore is not addressing adequately. Harry, having a strong sense of responsibility for his fellow students, may feel that the only way to ensure their safety is to remove Dumbledore from his position. He might believe that Dumbledore's actions or inactions are putting the students at risk, and thus he takes matters into his own hands.

Well, it could be that Harry has a different view on how to handle the war against Voldemort. Dumbledore is often very strategic and sometimes keeps things from Harry for what he believes is the greater good. But Harry might think that full transparency is necessary. Also, Harry may have formed new alliances or friendships that give him different perspectives, and these new ideas conflict with Dumbledore's. He might feel that Dumbledore's approach is too old - fashioned or risky in a new context.

One possible storyline could be that fem Harry has some sort of special power or ability that makes Dumbledore take her under his wing as a 'pet' in a sense of protection and mentorship. Maybe she has a unique connection to magic that he wants to nurture.

One possible reason could be Dumbledore's over - reliance on his own grand plan. He might have been so focused on the big picture of defeating Voldemort that he overlooked Harry's individual emotional and psychological needs. For example, Harry constantly had to face dangerous situations alone, and Dumbledore didn't always step in to protect him directly. This could have led to Harry feeling abandoned and having to grow up too fast without proper guidance in some aspects.