Why did Sora's Keyblade immediately look like Mickey Mouse?

I've played every game and even know a little of the outside-the-games lore but this has always confused me
His keyblade starts with the Kingdom Key keychain, drawing obvious references to Disney Castle with the kingly theme and Mickey's ears. Mickey himself has a Dark Realm keyblade that looks like himself, which makes a bit of sense
His keyblade should have come as a direct result of Terra bequeathing a keyblade to Riku, but since Riku was rejected, it went to Sora, so shouldn't it have been themed around Terra instead? Or even themed after his own life as an island dweller?

(and before you say it I know KH has a lot of working-around-older-games wonkiness, I was wondering if this specific one had an explanation I haven't seen yet lol)