Let's see, some dumb shit I've heard as a kid:

-There's a Rainbow Road stage in Mario 64 if you collect all the stars and use the cannon in the courtyard.

-Cloud Strife is a GF in FF8 that you can get if you defeat the secret ¨Omni Weapon¨ super boss.

-Crash Bandicoot is a secret playable character in Smash Bros Melee.