Activate the following game modes by performing the corresponding tasks. To revert back to normal, play the mode you activated a second time. Note: These may only work on the Wii U version of the game:
HOW TO UNLOCK
Gameboy Color Mode
Type in ARCADE MACHINE to get an arcade that can be played.
Type in VIDEO GAME to get a gameboy.
Old Timey Mode
Type in TIME MACHINE, and use it to make everything sepia tone, and have a piano bgm.
Whenever Maxwell dies from electrocution while wearing an item that changes his vision, the music will change into a simple retro midi theme upon continuihng. This can be done with the XRay Goggles, XRay Glasses, Nightvision Goggles, Thermal Goggles, or Polarized Sunglasses.