If we talk about the power within Charizard, aside from his own strength, it's the power inherited from Ho-Oh.
Even to this day, the Rainbow Wing exists within Charizard's body. Even though he has mastered the Divine Flame and reached the Gym Peak level, the Rainbow Wing still holds great significance for him.
This feather is definitely not just an ordinary feather that fell off Ho-Oh. It's a feather imbued with part of Ho-Oh's power. Ash estimates that this feather equates to what the big shots in the group refer to as a legendary beast medium.
Similar to the Green Treasure Pearl of Sky Dragon and the treasures of the Time-Space twin gods, if this feather fell into the hands of an evil organization, with the current technological development of the evil organization, they could perhaps create a machine to control Ho-Oh.
Thus, even until now, Ash never casually mentions having the Rainbow Wing. Only his closest acquaintances know about it.
But now Mewtwo says the GS Ball he holds contains Ho-Oh's power? Could it be that this is a Pokeball created by Ho-Oh?
The mystery remains intricate. Better take the GS Ball to Valencia Island to Dr. Nemu first.
Ash puts away the GS Ball, says goodbye to Professor Oak, and the three of them start heading towards Viridian City side by side.
The distance from Pallet Town to Viridian City is not far, but if they were to walk, they definitely wouldn't reach the airship by morning. So after leaving Pallet Town, Ash immediately releases Pidgeot to carry the three of them flying towards Viridian City.
Although Charizard can also carry people, it's not as efficient as Pidgeot. Carrying two people is about the limit for Charizard; any more and he would have to carry them with its claws.
Therefore, if they want to fly in the air, Pidgeot is the better choice.
It's worth mentioning that Ash currently has six Pokemon with him: Charizard, Pidgeot, Pikachu, Gardevoir, Mewtwo, and Lugia.
Even though Togepi is also brought along, it takes up Misty's slot. Now, Misty has fewer Pokemon, just Seadra, Dragonair, and Psyduck.
The reason they are going to the Orange Archipelago this time is mainly for vacation, but also to capture some Pokemon, so they intentionally reduced the number of Pokemon they carry.
As for Ash, it's hard to manage, since Charizard and Pidgeot are for emergency transport, Pikachu is a must-bring, Gardevoir refuses to be separated from him, and lastly Mewtwo and Lugia...these two Pokemon are obviously not possible to keep at Oak's Research Institute.
Ash foresees that this journey won't be easy. He drew three top-tier boosters in the group, and the first and second times he drew them, he soon encountered situations where they were needed.
The third time should be the same. On this journey, he might encounter an adversary so challenging that he needs reinforcements to handle.
Therefore, there's no way Ash will leave Mewtwo at Oak's Research Institute.
Moreover, he applied for the seventh Pokemon slot specifically for Mewtwo; it wouldn't make sense to now leave Mewtwo at the institute.
So Ash ended up with these six, while Misty has four, and Brock only brought Onix and Golbat, leaving the rest at the Gym for training.
Since the news of the Silver Conference spread, the pressure on each Gym has significantly increased, as Gym Badges from other regions can also be used to participate in the Silver Conference, leading to a mad rush in Gym challenges all over the region!
Whether it's Pewter Gym or Cerulean Gym, they've been facing a tremendous amount of challenges recently. Over at Pewter Gym, though Brock's father Flint might be a bit unreliable, he's still a veteran Gym Trainer.
With the Pokemon Brock provided, they can barely handle those challengers, but over at Cerulean Gym, the pressure is quite heavy...
This is also why Misty has even sent back her strongest Starmie; if she doesn't send more Pokemon home, her three sisters might get overwhelmed!
Even though she's been acting as the proxy Gym Leader for a long time, only Sayo truly has command level capabilities.
The other two sisters are still amateurs, and the only reasons they hold the position of Gym Leader are because Misty's Pokemon are strong enough and there's really no one else.
Originally, Misty was supposed to return during this period. Yes, Misty was supposed to go back without even reaching the Orange Archipelago, but once Sayo learned that Misty had a boyfriend and that the boyfriend was Ash, she immediately said Misty didn't have to come back yet.
For the sake of her sister's happiness and to give the couple more time during their honeymoon phase, Sayo resolutely took up the banner of the Gym. It's uncertain how long Sayo can hold on.
In any case, before Sayo can't handle it anymore, Misty can still spend some time with Ash as a couple. But as more challengers come, even if Sayo doesn't call Misty back, Misty will hurry back to Cerulean Gym.
Because she is the Gym Leader of Cerulean Gym!
Ten minutes later, Pidgeot successfully brought the three of them to Viridian City. While walking may have taken a day, with Pidgeot it's just a mere ten minutes, which is why Ash prefers to travel using Pokemon.