"Ash, you need to stop being such a kid," Iris muttered, rolling her eyes.
"Pika-chuu!" Pikachu said, flicking his ears.
"Yeah, I guess," Ash agreed. "Why do you keep calling me a kid?"
Iris stared at Ash.
"...Ash, we've been travelling together for two months," she said. "Why are you only asking now?"
Ash shrugged. "I guess I thought it helped you out to call me a kid more than it hurt me!" he replied. "Because, you know, I don't mind being called a kid, not much. I'm younger than Jessie and James are, right? They're, what, twenty-five or something like that, and I'm around…"
He frowned.
"Half that, I think? Maybe a bit more?"
"That's not what I was saying," Iris muttered.
"Then what were you saying?" Ash replied. "I did ask. But I think we're about the same age."
"It's not about age!" Iris replied. "It's about maturity, because you… you act like such a kid sometimes."
"Excuse me," James said. "But are we bothering you? We can come back later if you want."
"We most certainly can not!" Jessie declared. "Twenty-five? I never! I am a well-preserved fifteen, and don't you forget it!"
"Then how come you've been sayin' that since we teamed up?" Meowth asked. "I guess if you've been fifteen for eight years already another couple years don't matter that much-"
"You can shut up!" Jessie shot back. "Come back here!"
With Team Rocket occupied chasing one another around instead of threatening to steal their Pokémon, Ash shrugged.
"What's so bad about acting like a kid?" he asked.
"It's when you're… you're… ergh!" Iris muttered. "If you don't get it, what's the point in explaining?"
Ash leaned back, shrugging. "Maybe you could try for once, huh?"
Iris did a double-take.
"What?" she asked, intelligently.
"If you just keep calling me a kid without explaining whether that's a good or bad thing, then how am I supposed to know if it's a good or bad thing?" Ash replied, which he thought was a pretty good point all things considered. "Do you not like kids or something?"
"What?" Iris replied. "No, I – I just – it's, you don't take things seriously!"
Ash folded his arms. "Well, maybe they're things that don't need to be taken seriously? I take Pokémon seriously."
"Chuu!" Pikachu agreed, nodding.
"What do you think, Cilan?" Ash added, nodding over at where their companion was surreptitiously using a spare cooking knife to cut Pansage free of his bonds. "You're older than us, right? Do you think I act like a kid?"
"I – but-" Iris spluttered. "You can't ask Cilan, he's not mature either!"
"...the Rockets?" Ash suggested. "I could ask them?"
"Not them either!" Iris protested.
"Well, how should I act mature, then?" Ash replied. "I mean… I am a kid, right? I'm maybe getting to being a bit old for a kid, but if you can't point to anyone who's actually older who you think is mature then maybe that's a you thing?"
"That's just who's here right now," Iris mumbled.
Ash still looked thoughtful.
"...so maybe what you're saying is that I need to be more like you?" he asked. "Because, I guess I could do that, but I tried that once before and it sucked."
Iris shook her head and stared at Ash.
"...what?!" she asked.
"I don't mean because it'd be being like you!" Ash hastened to say. "Just that, back in Kanto I felt like doing really well in battles was really important, and when I lost my Indigo League battle because Charizard was being troublesome I… had real trouble coping with it."
He shrugged. "I guess maybe now I don't take that kind of thing as seriously, but I like it! It's better this way, or that's what I think at least."
Iris frowned, looking thoughtful.
"...I guess," she said. "Wait, you have a Charizard? And you never told me?"
"He lives with his girlfriend now-" Ash replied, then Jessie interrupted him.
"Wait!" she said, stopping halfway through giving James a noogie. "The twerps were trying to distract us!"
"It sounds like they were trying to work through their situation," James complained. "Why don't we do that more often? I think you – that is, we – could use therapy!"
"We ain't got the time or money for that!" Meowth replied, as if they weren't using a very expensive rope-net cannon and a lot of time to do what they were doing. "Now get to the capturin' their Pokémon already!"
AN:
"When I became a man I put away childish things, including the fear of childishness and the desire to be very grown up."
I think I'll agree with Clive Staples Lewis here.