A very creative take could be that Fem Godzilla is shrunk down to human size in the Naruto world. She then tries to live as a normal person but still has her Godzilla instincts. This would lead to some really funny and heartwarming moments as she tries to fit in among the shinobi, all while having the potential to turn back into her giant form at any moment.
One of the most creative ideas might be that the Naruto world is actually a part of Godzilla's world in a way. Maybe the tailed beasts are related to some ancient Godzilla - like creatures. In this fanfiction, Naruto and his friends have to uncover this mystery and deal with the implications.
A plot could be that Godzilla's DNA is used in some crazy experiment in the Naruto world and it creates a hybrid creature with ninja abilities. This new being has the strength of Godzilla and the stealth and jutsu skills of a ninja. It would be a very powerful and unpredictable character in the fanfiction.
In some fanfiction, Godzilla could be a guardian of a hidden magical realm within the Harry Potter universe. This realm contains powerful magic that could be used for good or evil. Voldemort tries to gain access to this realm to get more power, but Godzilla stands in his way. Harry and his friends then have to decide whether to help Godzilla protect the realm or try to find a way to use the power within for their own fight against Voldemort.
A very creative 'Naruto' fanfic idea could be a time - travel one. For example, Naruto travels back in time to prevent the Uchiha massacre. Another idea is a fanfic where the ninja world is merged with the fairy - tale world. So Naruto could be fighting against the Big Bad Wolf or teaming up with Cinderella. And a fanfic where the Sharingan has a completely different power, like the ability to control the weather, would also be a very creative concept.
Perhaps Naruto is initially unable to control Godzilla properly when he first summons him. This causes chaos as Godzilla goes on a rampage, but Naruto then has to figure out a way to communicate with Godzilla on a deeper level to stop the destruction and turn him into an ally. This adds a layer of complexity and character growth to the story.
The concept of bringing the villains from both universes together is also quite creative. For example, Orochimaru and Lord Farquaad teaming up against Naruto and Shrek. It creates a whole new dynamic and a lot of interesting plot twists as the heroes have to figure out how to defeat this unexpected alliance.
One creative idea is a time - travel fanfic where Holo travels to the Naruto universe during a crucial moment in the ninja world's history. Her presence changes the course of events in unexpected ways. For example, she might use her knowledge and charm to broker peace between warring clans.
Some fanfictions have the concept of Naruto being a long - lost relative of Daenerys' family. This idea is quite out - there but it allows for a lot of creative storytelling. It can lead to Naruto having a claim to the Iron Throne and a whole new set of adventures as he tries to help Daenerys claim her rightful place while also dealing with his own new - found heritage.
Perhaps in some fanfictions, Naruto is the only one who can see Tinkerbell in the Naruto world. So he has to keep her a secret while also using her help to solve various problems in the Hidden Leaf Village. This idea plays on the idea of Naruto being an outcast at first and now having this unique secret.
The concept of using shadow clones in GTA - style heists is very creative. The clones can be used to distract the police or perform multiple tasks simultaneously during a robbery. Another creative idea is when the characters from Naruto have to deal with the moral ambiguity of the GTA world. For instance, Naruto, who is known for his strong sense of justice, has to navigate through the seedy underbelly of the GTA world, which often challenges his beliefs and values.
One creative idea is using alchemy to revive the dead in the Naruto world. It could bring back characters like Minato or Itachi, but with a twist because of the alchemical process. This would completely change the story's direction.