If you ever see one in your party or PC box, turn off your game and DON'T SAVE. If you did save, turn off the game, remove the hacking device, turn on the game, and put the Bad EGG into a PC box. Use a code to put a Pokemon (doesn't matter which) into the box and slot that the egg is in, overwriting it. If you have more than one Bad EGG, it's either because you didn't remove the hacking device when you were supposed to (fixed by overwriting each egg) or because the egg is of a variety (yes, there are multiple types) that has damaged your game (which is VERY bad). Oh, and DON'T LEAVE YOUR PC UNTIL YOU DON'T HAVE ANY BAD EGGS.
If you are unable to complete any of these steps, it is likely that your save file (or even the game itself) is permanently damaged. If the egg hatches (some types do, while others don't; this is why you need to get it out of your party), it's almost certain that your save file is lost, and your game may never work again. This is why you should always use extreme caution when using cheat codes.
(Note: I have heard of one case in which someone dropped his game and a Pokemon had turned into a Bad EGG when he loaded his save file. Although this is possible, it's extremely improbable.)
7 years ago