To active cheats, in the main menu, hold down the shift key and type MENSAAAA and you'll hear "thats what I need." After that, during the game you can type the following cheats:
Code - Result:
LShift+LCTRL+A - Skip Level
LShift+LCTRL+R - Restart Level
LShift+LCTRL+C - Continue if Failed Mission
G - God Mode

Skeleton Play
Enter Neon's profile in the characters menu and type in the code "ZIOCLETO", once you reach a mission with neon, you will play the mission with his skeleton.