Perhaps Harry Potter takes Jonathan Crane to Hogwarts. There, Crane could learn about the different magical creatures and how they deal with fear. For example, the boggarts can transform into one's greatest fear. By observing how students at Hogwarts face their boggarts, Crane could gain new insights into fear and how to overcome it. Also, the calming atmosphere of Hogwarts, with its magic and sense of community, might have a positive effect on Crane's mental state.
One scenario could be that Harry uses his invisibility cloak to help Crane study his patients without being noticed. This would allow Crane to get a more accurate understanding of their behaviors.
One common scenario is during the Triwizard Tournament. Maybe Fleur is struggling with a task, like the second task in the lake. Harry, having already completed it, could give her some tips on how to find the hostages or deal with the merpeople. Another scenario could be when Fleur is facing some form of discrimination or bullying at Hogwarts or in the wizarding world. Harry, being a champion of justice, would step in to support her.
One common scenario is Snape helping Harry with his Potions work. Since Snape is the Potions master, he might offer some extra guidance to Harry, which could be crucial for Harry's progress in school. Another scenario could be Snape protecting Harry from the bullying of other Slytherins. He might not do it in an obvious way, but still intervenes subtly.
Well, Harry Potter could use his magic skills to help Jonathan Crane face his inner demons. Maybe he could use a spell to calm Crane's fear-induced madness.
In fanfiction, a possible scenario is that Harry Potter, with his ability to understand and manipulate magic, helps Lyanna Stark to unlock some hidden magic within herself. This new - found magic could give her an edge in the political and dangerous environment of Westeros. He could also bring her to Hogwarts for a short while (in the fanfiction world's rules), where she could learn from the professors and gain knowledge that she can apply back in her own land.
One common scenario is when Harry is in trouble at Hogwarts. Sirius might break into the school in his animagus form to rescue Harry. Another is when Harry is dealing with the mystery of his parents' death. Sirius can share memories or information that he has about that time, like what really happened the night they died. He can also help Harry deal with the Dementors, as he has his own experiences with them.
One scenario could be after a particularly difficult encounter with a Death Eater. Harry is shaken and full of self - doubt. Ginny takes him to the edge of the Black Lake. They sit there, and Ginny just holds his hand, letting him know she's there. The peacefulness of the lake and Ginny's silent support start to soothe Harry.
In a more complex scenario, Bellatrix could be trying to use a dark magic ritual that would cause great harm to the wizarding world. Harry discovers her plan and has to engage her in a magical struggle. In the process, he manages to turn her own dark magic against her, which results in her death. This would show Harry's ingenuity and his ability to use the enemy's own weapons against them.
Another scenario could be in the hallways. Malfoy might be with his cronies, and they're bullying other students. Harry squints as he decides whether or not to step in and confront Malfoy. It's a moment of decision - should he get involved or let it pass? And the squint is a physical manifestation of his internal debate.
One scenario could be when he's in the Forbidden Forest. He's been out there for a while, perhaps on a secret mission, and he hasn't had a chance to eat. His stomach growls, and it might even attract the attention of some of the forest's creatures. It would create a tense moment as he has to deal with both the threat of being discovered and his hunger.
Well, one possibility is that in fanfiction, Death Eaters who survived the war might capture Harry Potter and experiment on him to extract the power of his connection to Voldemort. They might believe that this power could be harnessed for their own evil purposes. Also, there could be fanfictions where rogue wizards from other countries experiment on Harry, seeing him as a unique specimen due to his fame and his defeat of the most powerful dark wizard in history.