Well Anime!Misty can't age either,but Game!Misty does age in GSC...but I can bet you already know that xD
I guess we all have to accept that Ash will never grow up and he's going to be trapped in a time loop...forever? sometimes I think the designers modified his eyes on purpose to make him even more "kidish" than he already is and not to update his design with Sugimori's current artwork :(
F*cking always loved mature Kasumi. The GSC hairstyle of hers was so attractive. I feel more sad for pokemon special Kasumi as her love for Red doesn't seem to reach and Yellow's relationship seems to be stronger with Red, even if Red doesn't see both as lovers.