I think Ben and Erza would make a great pairing. Erza is a very disciplined and powerful mage. Ben with his Omnitrix could learn a lot from her in terms of strategy and self - control. On the other hand, Erza would be fascinated by Ben's alien forms and their unique abilities. They could team up in battles and Erza might even give Ben some tips on how to better handle his powers in the magical world of Fairy Tail.
Lucy and Ben could be an interesting pairing. Lucy is a Celestial Spirit mage, and she has a very kind and curious personality. Ben, with his experiences from different planets and his alien forms, could share a lot of stories with her. In a fanfic, they could go on adventures together, with Lucy using her spirits and Ben using his aliens to overcome obstacles. Also, their friendship could grow as they learn more about each other's worlds.
Definitely Naruto and Natsu. They are both the main protagonists in their respective series and have a lot of energy and a strong sense of justice. Their interactions would be really fun to read, like when they compete to see who can defeat the most enemies or who has the stronger fire - related power.
Lucy from Fairy Tail and Rin from Fate could form an interesting duo. Lucy is a Celestial Spirit mage, and Rin is a skilled mage in her own right. They could bond over their shared love for magic and their determination to protect their friends. They might also exchange knowledge about different types of magic, with Lucy showing Rin her Celestial Spirit magic and Rin introducing Lucy to some of the more unique spells in the Fate universe.
Ben and Natsu would be an interesting pairing. Natsu is all about fire and brute strength, while Ben has the ability to transform into various aliens with different powers. They could have a friendly rivalry, like who can defeat an enemy faster. Ben could show off his alien forms to Natsu, and Natsu could teach Ben some fire - based magic tricks in return.
Asta and Natsu would be an interesting pairing. Asta's anti - magic and Natsu's dragon slayer magic are polar opposites. They could have some really cool battles and also learn from each other. Another good pairing could be Lucy and Noelle. Lucy has her celestial spirits and Noelle has her water magic. They could bond over their magical abilities and their insecurities as mages. And then there's Gray and Yuno. Gray's ice - make magic and Yuno's wind magic could create some interesting combined attacks or strategic plans during a fight.
I think Natsu and Ruby would be an interesting pairing. Natsu is impulsive and powerful with his fire magic, while Ruby is young and enthusiastic with her scythe skills. They could bond over their love for adventure and their desire to protect their friends. They might also learn new ways to fight from each other, like Natsu learning about Ruby's speed and Ruby learning about Natsu's raw power.
Lucy and Albedo could also make for an interesting pair. Lucy is a strong - willed mage with her own set of celestial keys, while Albedo is extremely loyal to Ainz. Their interactions could explore themes of loyalty and friendship, as Lucy tries to understand Albedo's devotion to Ainz while also showing her own loyalty to her Fairy Tail friends.
Lucy and Eevee could be an interesting pair. Lucy is kind - hearted and Eevee is a very adaptable and cute Pokemon. Lucy could use her celestial keys to help Eevee evolve into different forms depending on the situation they are in. For example, if they need to cross a large body of water, she could help Eevee evolve into Vaporeon.
Natsu and Ziva would make an interesting pairing. Natsu's hot - headedness and powerful fire magic could contrast well with Ziva's cool and efficient combat skills. They could learn from each other in terms of fighting styles and also develop a friendship based on mutual respect.
Natsu and Mr Smith could be an interesting pairing. Natsu's brash and fiery personality combined with Mr Smith's cool and calculated demeanor would create some great comedic and action - filled moments. Natsu could learn some strategic thinking from Mr Smith, while Mr Smith could be amazed by Natsu's raw power.
Naruto and Natsu would be an interesting pairing. Naruto is full of energy and determination, and Natsu has a similar fiery spirit. They could compete in friendly challenges, like a race or a strength test. Another great pairing could be Sakura and Erza. Sakura is a strong - willed and capable kunoichi, and Erza is a powerful mage. They could share stories about their training and experiences in combat.