One possible plot twist could be that Pikachu suddenly loses its ability to use electric attacks. This would completely change the dynamic of the battle as Pikachu would have to rely on physical attacks like Quick Attack, which might not be as effective against Bayleef. Another twist could be that Bayleef evolves during the battle into Meganium, gaining new and more powerful abilities that catch Pikachu off - guard.
In such a fanfic, Pikachu might use its electric attacks like Thunderbolt. Bayleef could counter with its grass - type moves such as Razor Leaf. Maybe Pikachu's speed gives it an edge in dodging Bayleef's attacks at first. However, Bayleef's sturdy build could help it withstand Pikachu's electric shocks. The battle could be very intense with both Pokemon trying their best to win.
The most exciting part could be when Pikachu uses its most powerful move, like Volt Tackle, against one of Ash's really strong Pokemon like Greninja. The clash of their attacks, with Pikachu all charged up and Greninja ready with its Water Shuriken or some other powerful move, would be intense. The build - up to this moment, with both Pokemon sizing each other up and the anticipation of which move will land first, would be really thrilling.
The change in its appearance can make it scary. For example, if its usually cute yellow fur turns dark or if its bright red cheeks become a sinister red glow. Also, if it starts to behave in an uncharacteristic way, like making menacing noises instead of its usual cute sounds.
Obviously, the main characters are usually Pikachu. But sometimes, there could be other Pokémon that play important supporting roles. For instance, a Pichu could be a sidekick or a younger Pokémon that the Pikachus are protecting.
One interesting plot could be two Pikachus from different regions meeting and learning about each other's unique electric attacks. For example, one Pikachu might know a special move that the other has never seen before. They could then teach each other and become stronger together.
Pikachu would probably win. It has been with Ash from the very beginning and has a lot of battle experience. Also, Pikachu has shown that it can adapt to different battle situations quickly. Ash's Pokemon are strong, but Pikachu's speed and electric attacks are hard to counter. It could use its speed to dodge attacks and then quickly strike back with a powerful Thunderbolt or Volt Tackle.
Naruto would probably be really excited. He'd treat Pikachu like a new friend and teammate. He might try to learn all about Pikachu's powers and how it can help in battles. For example, he'd be eager to see Pikachu use Thunderbolt in a fight against an enemy ninja.
Lucario is also a popular choice to be paired with Pikachu in crossovers. Lucario has its own unique abilities related to sensing and combat. When combined with Pikachu's electric attacks, they can form a formidable team. The contrast between Lucario's more serious and stoic nature and Pikachu's cute and energetic personality also adds depth to the story.