Well, in some fanfictions, he could be a new threat that emerges from a portal. The portal could be a result of some of the wacky experiments in the Adventure Time world. He might start causing mayhem and the heroes, like Finn and Jake, have to figure out how to stop him.
He could also be a creation of a mad scientist in Adventure Time. For example, if Princess Bubblegum's experiments go wrong, she could accidentally create Jeff the Killer. This would put her in a moral dilemma as she tries to figure out how to deal with her creation while also protecting the Candy Kingdom and the rest of the Land of Ooo from his murderous tendencies.
Finn would likely be a very determined participant. His strong sense of justice would make him oppose the killing game wholeheartedly. He might try to find a way to escape and take as many people with him as possible. Jake, on the other hand, could use his shape - shifting abilities to protect himself and others. He could turn into a shield or a large beast to fend off attackers.
The main difference is the form. The original Jeff the Killer is a full - grown, menacing figure. In the baby fanfiction, he's in a baby form which completely changes the dynamic. It's like comparing a big, scary wolf to a baby wolf. Even though they may share some traits, the perception is very different.
Frank Sinatra could be depicted as a suave, dapper figure in the Adventure Time universe. He might wear a sharp suit, like his real - life style, but with a bit of an Adventure Time twist, perhaps with colorful patches or strange buttons. His hair would be slicked back, and he could have a magical microphone as his weapon or tool.
One interesting fanfiction could be where Jeff the Killer somehow ends up in the Adventure Time universe and has to face off against Finn and Jake. Maybe he initially tries to cause chaos but then realizes that the magic and unique characters in Adventure Time are more than he can handle.
Another way Cerberus can fit into the Naruto world in fanfiction is as a spiritual guide. Maybe Naruto, during a near - death experience, enters a spiritual realm where he meets Cerberus. Cerberus then guides him on a journey to discover new powers within himself. This could be related to Naruto's connection with the nine - tailed fox and how Cerberus helps him better understand and control that power.
In fanfiction, umbramancy can fit in by being a long - lost or forgotten magic. It could be something that was once used by ancient wizards but lost over time. For example, it might be rediscovered in the Forbidden Forest by a curious student.
Nyarlathotep could be a new, powerful and malevolent force that disrupts the balance of the Harry Potter universe. He might be an entity from a different dimension that finds its way into the wizarding world, causing chaos.
Perhaps she is a time - traveler in the fanfiction and ends up in the past with the Black family. There, she uses her modern knowledge to navigate the complex family dynamics and even influence their future. For instance, she could prevent certain family members from making bad decisions that would lead to the family's downfall.
Cortana might be seen as a powerful magical tool in the Harry Potter fanfiction world. Some might write that she has the power to enhance a wizard's magic. Imagine a wizard using Cortana to boost the power of their spells. She could also be used to store magical knowledge, like a magical hard drive, and wizards could access this knowledge to learn new spells or techniques.
In fanfiction, the Ebon Hawk can fit by being a mysterious new element. It could be a ship that arrives in the Naruto world from another dimension, bringing with it new powers and technologies that the ninjas are both intrigued and cautious about.