How exactly do those letters get into the mailbox, considering where it is?
That is what bugs you about the game world? Seriously?
Fandon decided the letters are delivered via Klaybird.
Where are those radio signals being broadcast from? From inside the 'Hood? If so, then who put them all together? Especially considering that The Neverhood seems to be a relatively young place. If they're from the outside, how close are they, really, to the nearest... er... Quatar-son-relm?