In some fanfiction, it could be that the NCIS has a connection to an ancient magic society that has ties to the wizarding world. When they hear of Harry Potter's plight, they draw on the resources and knowledge of this society. They might use special potions or spells that they've obtained through this connection to protect Harry from the threats he faces, like Voldemort's curses or the attacks of his Death Eaters.
Another possibility is that there is some sort of crossover magic. Maybe a spell goes wrong and links the NCIS world to the Harry Potter world. The NCIS agents, being the resourceful people they are, quickly adapt to the situation. They learn about the danger Harry is in, perhaps from Hermione who has some knowledge of both worlds now. Then they use their own brand of justice and skills to save Harry from whatever dark forces are after him.
One common scenario could be Harry being framed for a crime he didn't commit. NCIS steps in to investigate and realizes the truth, thus saving Harry from unjust imprisonment.
In fanfiction, it could be that the NCIS has some sort of magical knowledge or artifacts. Maybe they've been dealing with cases that are on the fringes of the wizarding world without realizing it. When they discover that Harry Potter is in danger, they use this knowledge or these artifacts to save him. For instance, they could have an ancient amulet that can counter dark magic spells aimed at Harry.
In some fanfictions, Harry might be saved by NCIS through their excellent investigative skills. They could uncover a plot against Harry in time, using their resources to track down the bad guys before any harm comes to Harry.
One possible scenario could be that Tony sacrifices himself to save a teammate during a dangerous mission. Maybe he takes on a bomb - defusing task and runs out of time, dying heroically.
Well, one possibility could be Itachi as a wizard in the Harry Potter world. Maybe he'd be in Slytherin due to his cunning nature. He could use his Sharingan abilities in a magical way, like seeing through invisibility cloaks or detecting hidden spells.
One possible scenario is that Harry Potter helps the giants when they are being hunted by dark wizards. He uses his invisibility cloak and other magical items to hide the giants and lead them to safety. Another scenario could be that he helps the giants who are sick. He might search for rare magical herbs to cure their diseases.
Maybe Harry would be able to use the Speed Force to time - travel within the wizarding world. He could go back in time to prevent certain tragedies or gain more knowledge about magic from the past. This would add a whole new layer of complexity and adventure to the Harry Potter story.
One possible scenario could be that Harry feels betrayed by Dumbledore for some reason. Maybe he discovers some secrets that Dumbledore has been keeping from him, like the true nature of his family's past or the real intentions behind certain events at Hogwarts. So, in a fit of anger and disillusionment, he decides to ignore Dumbledore.
Perhaps in the fanfiction, Harry Potter's death occurs because he tries to rewrite a powerful magic spell that goes horribly wrong. He was always known for his bravery and willingness to take risks in the original series, so this could be an extension of that. His death would then be a tragic consequence of his own curiosity and desire to push the boundaries of magic.
One scenario could be that the Winchesters are trapped in a magical dimension while on a hunt. Harry Potter, with his experience in navigating strange magical places, could find a way to enter the dimension and lead them out. Another possibility is that a powerful dark wizard has set a curse on the Winchesters. Harry, being well - versed in counter - curses, would be able to break it and save them.