Misty and Brock were essential elements of the Pokémon anime, almost from the moment they first appeared on-screen. However, they weren't just there to keep Ash company--they played a very important role in Ash's character development, as evidenced by a small scene from early on in the series.

Ash in the beginning of the series is a very different character from the one he would eventually grow into. Ash was often clueless about basic things, and didn't exhibit much in the way of empathy, having a tough time understanding others. He's hot-headed, to the point where he occasionally attacks people with his fists, and he's liable to let things like grudges and rivalries control him. That's nothing like the calm, mature Ash that fans see in Pokémon Journeys, the last series starring Ash. But Ash never would've become like that if it weren't for the influence of Misty and Brock.

Misty and Brock Help Ash Recognize His Shortcomings

The Two Trainers Point Out Where Ash is Struggling

Brock is older than Ash by a fair amount, while Misty is just a bit more mature and experienced than Ash is at the start of the series. Ash himself is pretty sheltered, not really understanding what life outside of Pallet Town is like. While he dreams of being a Pokémon Master, he doesn't really understand what that entails, and sets off ill-prepared for what's to come. Ash absolutely needed Brock and Misty to tag along with him, to help with things like preparing food and finding safe places to camp.

Ash's lacking emotional maturity is almost as big of an issue, though. It's evident from the first episode, where he struggles to connect with Pikachu and resorts to literally dragging him around on a rope. He doesn't have much problem with destroying Misty's bike, either, never really considering how she would react. Ash winds up with Misty as a direct result of his lack of maturity, which, ironically, is probably the best thing that could've happened to him. It doesn't take long after Misty shows up for Ash to start learning from his mistakes, either.

In "Water Flowers of Cerulean City," during Ash's battle with Misty at the Cerulean gym, he uses Butterfree to paralyze Staryu, prompting Misty to exclaim her concern. Ash mocks that concern, asking how she even knows it's in trouble, to which Misty responds simply: "Because I'm sensitive to other's feelings." Ash again mocks the idea, saying "Like I'm not." Except... he isn't. While Ash clearly cares for Pikachu at this stage, he still has a hard time extending the way that he feels about Pikachu to other people and Pokémon. Ash doesn't quite learn his lesson here, but it calls to the audience's attention that Ash has some growing to do.

Misty and Brock Taught Ash Important Lessons

Ash's Companions Existed to Teach Him to Be Better

They don't just point out where Ash is having a hard time, however. Misty and Brock will often teach Ash important lessons, especially when he's letting victories go to his head. In "Mystery at the Lighthouse," Ash begins bragging about his accomplishments, to which Misty and Brock are quick to remind him that both their gym battles were unusual situations, and that most of Ash's Pokémon ed him of their own volition, rather than being captured due to his skill. They even teach him about the limit of six Pokémon, which one would expect Ash to be familiar with.

But Brock and Misty's lessons for Ash are more than just how Pokémon work. In "Bye Bye Butterfree," Brock and Misty help Ash to learn that Butterfree must be released, so that it can mate and live a full life. This is the first moment where Ash has some serious character growth, doing the mature thing and releasing Butterfree, despite how much it hurts. If Ash were traveling on his own, he may not have even thought about releasing Butterfree, but Brock and Misty make it clear to him how important this is.

Misty and Brock are also there for Ash when he's feeling down, however. In "Primeape Goes Bananas," Misty consoles Ash after he learns how far ahead the other trainers from Pallet Town are, emphasizing to him that he doesn't have to compare his journey to that of others. Brock states that while Ash may have fewer Pokémon, he's managed to procure quality Pokémon, and that's worth a lot. These lessons are a bit wasted on Ash in the moment, but they're valuable things to learn all the same.

Misty and Brock Made Ash Who He Is

Ash Grows Thanks to Misty and Brock's Influence

Ash has a hard head, and it sometimes takes a while for Misty and Brock's lessons to sink in. Still, they undoubtedly contributed a lot to Ash's character growth. Ash goes from not understanding why Misty would be upset that her Pokémon is hurt to standing up for Pokémon who are being victimized. Ash would go on to risk his life defending or attempting to rescue Pokémon, such as the many times he's leapt off a cliff to save a falling Pokémon.

By the time of Pokémon Ruby and Sapphire, when Ash has parted ways with Misty, he's grown tremendously, both as a trainer and a person. He's no longer trying to fight people, and has mellowed out substantially, no longer so insecure about his progress. When he begins traveling with May, it's now Ash that is the experienced trainer, able to impart the lessons that he learned from Misty and Brock to May.

Misty's, and especially Brock's, influence on Ash led him to become a better person, one who can understand different viewpoints without resorting to violence, and who's come to understand that other people can have bonds just as strong as his with Pikachu. It's fair to say that Ash never would've stood a chance of becoming world champion without the lessons that Misty and Brock imparted on him, preparing him to become that more mature trainer who faced off with Leon. Misty and Brock were essential to Ash's growth in Pokémon, and that's something that can't be denied.