If we think about it, Naruto's shadow clones could be used in interesting ways in the Sailor Moon universe. He could send his clones to gather information about the villains while the Sailor Guardians are preparing their attacks. Luna's ability to communicate with Sailor Moon could be extended to also communicate with Naruto's clones. Also, Sailor Moon's transformation powers might be able to affect Naruto in a way that gives him a temporary boost in speed or strength similar to when she transforms.
In a fanfiction scenario, Naruto's Rasengan could be combined with Sailor Moon's Moon Tiara Action. Maybe Naruto creates a Rasengan that has the power of the moon infused into it with Luna's help. This new attack could be extremely powerful and could be used against powerful enemies. Also, Sailor Moon's healing powers could be used on Naruto when he gets injured in battle, and in return, Naruto could use his ninja skills to protect Sailor Moon and Luna when they are in danger.
Naruto's ability to use chakra could be combined with Sebastian's demonic powers in interesting ways. For example, Naruto could use his chakra to enhance Sebastian's physical attacks. Or Sebastian could use his knowledge of the supernatural to help Naruto better understand and control his bijuu chakra.
Well, Naruto has his Rasengan, a powerful spinning ball of chakra. Ultear could use her time - magic to age or de - age the target area where the Rasengan is about to be launched. If she ages the area, it might make the ground harder, increasing the impact of the Rasengan. Or if she de - ages it, she could create a soft, muddy area that would trap the enemies in the Rasengan's path. Also, Ultear's ability to see into the future could help Naruto anticipate his opponents' moves better, allowing him to use his ninja skills more effectively.
Naruto's shadow clone technique could be combined with Goku's ability to split into multiple versions of himself during the Kaioken technique. This would create a horde of super - powered clones that could overwhelm opponents. Also, Naruto's Rasengan could be infused with the energy of a Ki blast, making it even more powerful. And Goku's Instant Transmission could be used in combination with Naruto's speed to create an unbeatable movement ability.
One possible storyline could be a crossover where Naruto's world is threatened by a villain from the Sailor Moon universe. Luna could play a key role in guiding Naruto and his friends, perhaps using her knowledge of magic and the Sailor Guardians. Another idea is that Naruto somehow gains Sailor Moon - like powers and has to learn how to use them in his own world.
Naruto's ability to use chakra and his powerful jutsu like the Shadow Clone Jutsu could be combined with Hanabi's Hyuga clan techniques. In the Sekirei world, they might use these combined abilities to take on stronger opponents. For example, Naruto could create clones to distract enemies while Hanabi uses her Byakugan to find weak points and strike.
Naruto's ability to create shadow clones could be used in strategic ways in Rias's battles. For example, he could send clones to scout out the enemy while the devils in Rias's harem set up their attacks. His Rasengan could also be combined with the devil's energy - based attacks. Maybe a devil could enhance the power of the Rasengan with their own magic. Also, Naruto's chakra control could help the devils in Rias's group to better control their own internal energy sources, as chakra control is a very refined skill in the 'Naruto' universe.
A lot of the time, Doomguy's indomitable will and his combat experience in the face of demons can be paired with Naruto's ninja skills. Picture Doomguy charging into battle, and Naruto using his wind - style jutsu to enhance Doomguy's attacks, like making his melee strikes even more powerful with gusts of wind.
Well, when it comes to combining their abilities in fanfiction, it's all about creativity. Naruto's ability to sense danger using his chakra could be linked with Astolfo's precognitive abilities (if he has any in the fanfic). This way, they could anticipate their enemies' moves even better. Also, Astolfo's charm - based abilities could potentially be used to sway some of Naruto's more stubborn opponents, while Naruto's raw power could back up Astolfo in a fight.
Some characters might laugh. If the fanfiction has humorous elements, like a comical take on their battles or relationships, they would find it entertaining. For instance, if there's a fanfiction where the Sailor Scouts accidentally swap powers and get into all sorts of wacky situations, the characters themselves might chuckle at the absurdity.
The bending abilities from Avatar: Pandora could combine with Naruto's chakra - based ninjutsu in interesting ways. For instance, a water bender could enhance a water - style ninjutsu by adding their unique bending style to it, making it more powerful and fluid.