Quote Originally Posted by Ryaan1234 View Post
Nintendo tends to keep all their prototypes, so they are usually as rare as hen's teeth, in comparison to everyday third party ones.
They're actually more common than you would think (at least from a prototype perspective). There are known prototypes of Zelda, Zelda 2, Mario 2, Mario 3, Yoshi, Tetris, Tetris 2, Wario's Woods, Kirby's Adventure, Pinbot, Dragon Warrior, and Dragon Warrior 3. That's just off the top of my head, and that's only including the NES (there are a ton of examples for the SNES).

Some third party companies actually kept a better lock on their stuff oddly enough.