Codes are largely a forgotten element of video gaming. They started out as debug features that didn’t get removed before release, then they became easter eggs to reveal to favored players, ways to dispense unlockables, ways to provide extra difficulty balancing, and even publicity tools, before the age of DLC gave developers a way to profit off of bonus features. Why have players enter up-up-down-down-left-right-left-right when you could just sell them play advantages outright. I’m simplifying the situation a bit, sure, but I’m not simplifying by much.
Codes still exist, once in a while, but it seems like they’ve gone back to being development aids. One of them crept into New Super Mario Bros. Wii, but only becomes usable if the game crashes. The code is: Home, Minus, Plus, Minus, Plus, 1, 2, 1, 2, A. It brings up a scrollable register dump and stack trace, and other assorted information. It doesn’t let you continue playing. For players, it’s just a curiosity, but it’s a thing that is interesting.
This video shows it off:
New Super Mario Bros. Wii Exception Handler (Youtube, two minutes)