The original game had the plates spell "It's kind of like Metroid", but in the room just to the right of the beginning, it says "It's kind of like Mother".
Also... you can get stuck. I opened a green door that would lead me back to the beginning, and you don't get a replacement key to open the last door. Either put 1 green door on each floor with one key, or make sure you can't do something stupid like that.
Sequel's in the works! :) www.isawhergame.com