Many "Developer Notes" evolved into hardcoded button combinations (like the famous Konami Code) that remained in the final retail version of the game.
Within the game's source code, developer notes (comments) often explain how a cheat functions or warn other programmers about potential crashes if a specific cheat is activated. Notable Examples Cheat Developer Notes:
Originally a developer tool for Gradius on the NES because the game was too difficult for the creator to finish while testing. Cheat Developer Notes: