Definitely Naruto. Naruto would be curious about Kirby's abilities and would probably want to be friends right away. They could have some fun training sessions together, with Kirby showing off his inhaling skills and Naruto his new Rasengan variations. Also, Sakura might interact with Kirby. She could be initially a bit skeptical but would come around when she sees how Kirby can be helpful in medical situations by using his powers to quickly gather medicinal herbs or supplies.
In such fanfiction, Kirby is often depicted as his cute, round self, but with a more tender side when it comes to his feelings for Jigglypuff. He might use his unique abilities to protect or impress Jigglypuff.
Another possibility is that one of the other characters in PLL has a hidden motive. For instance, someone who is jealous of Allison's popularity or someone who she had an argument with in the past. They might have found a way to make her sick without being suspected at first.
It depends on the context and development of the story. Sometimes love alone can overcome many challenges, but in other cases, external factors might play a role.
Ruby could be a great friend for Kirby. They both have a sort of innocence about them. Ruby's love for adventure and her kind heart would make her open to befriending Kirby. They could go on adventures together and Ruby could help Kirby understand the world of Remnant.
It has likely influenced the franchise in terms of art direction. The Japanese graphic novel's art style may inspire future Kirby games or other media in terms of character design and scenery. For example, if the graphic novel has a particularly cool way of depicting Dream Land, it could be incorporated into a game.
Well, in such a fanfiction, game Kirby could introduce anime Kirby to the more traditional power - ups from the games. Meanwhile, anime Kirby could show game Kirby some of the unique storylines and character interactions that are common in the anime. Maybe they would have a friendly competition to see who can inhale and defeat enemies faster. It would be a really interesting crossover with a lot of potential for fun and adventure.