I've noticed it myself in some of the scenes before they go to the realm of sleep that they look as they did in KH2 (minus Riku's cut hair). When in the realm of sleep Sora face looks more young like in KH1. And Riku seems slightly smaller than in KH2. I know that no one can truly know the exact reason at this point but I'm interested in knowing what you guys's theories are.

Yeah, i have noticed that. Could be the clothes

They have to learn how to use the Keyblade from the beginning, in the "proper" way. That affected their physical aspects.

Because Square has a deep seeded fear of anyone over the age of twenty, leading them to worship the age groups of thirteen to 18 and to find excuses to make people younger, such as the rather unecessary contrivance of making Riku and Sora their original younger selves.

Dave's probably right.

 

I think it might have something to do with the concept of dreams. Dreams makes us feel lighter, and stronger than we actually are, hence, the aerodynamic sense of traveling that we keep seeing in the previews. We often feel better about ourselves in our dreams, and maybe being 'younger' is a way to show that.

 

It could also have to deal with the fact that Namoura really likes Sora's KH1 model

Maybe he looks better like that.

yen sid reverts them to there original state from kh1 in order to learn the true art of keyblade mastery

Oh wow, I'd never thought this question would appear again, especially since the release is so close . But yeah, like everyone is saying, the reason they look so young is because they have to start over to properly use the keyblade.

 

Because Square has a deep seeded fear of anyone over the age of twenty, leading them to worship the age groups of thirteen to 18 and to find excuses to make people younger, such as the rather unecessary contrivance of making Riku and Sora their original younger selves.

 

LOL true >w<

well i think they look younger because they had to learn to use the keyblade from the very beginning so they probably aged back a couple years but the new clothes no idea.

they propably dream about getting younger. Even i dream about being a kid again

Because Nomura is running out of reasons for them to start at lvl 1

All of the reasons stated above

Its said that its because they are learning how to properly weild the keyblade from the begining, to become masters.(Because unlike the BBS characters, who were instructed by their master, Sora and Riku self-taught themselves to use the keyblade) So they take on their younger forms, in a sense, kind of going back in time and starting over.

BECAUSE THEY ARE IN THE *censored* DREAM WORLD!!! WHY DO YOU NOT GET THIS?!?

I guess they have to train to use the keyblade from the exact point they gained the power to use it, that would explain why Sora looks the same as he did in KH1 and Riku looking between KH1 and KH2 as he didn't realy gain the power to use a keyblade until after CoM (the 'Way to Dawn' keyblade was first introduced in KH2 so he got it after leaving Castle Oblivion).