Wacky quests, in-jokes and more

You activate an old jukebox hidden somewhere in game that plays the audio from this: Already There

A random Ding Squirrel somewhere.

Checkerboardland! (like a Disneyland with nothing in it but a checkerboard floor, lol)

Selfish request:
A small, hidden nod to a small band of NCOs that were like a family (no specific names necessary)