Debugging is both. It's simply opening up the back of any U.S. Tamagotchi and rubbing a pencil between two, small semi-circles, thus unlocking Hypertime mode (your Tama moves super-fast with the press of the C button) and character select (as soon as the egg hatches, you can scronn through characters with the A button).
Some people say that debugging is good and cool because it unlocks a whole new dimension of your Tama and allows you to see previously not-obtainable characters (with debug, let's just say you can raise Nazotchi and then some).
Some people say it's bad because it could break the Tama (some people pull the sound wires lose or scratch the chip, or rub the two circles off) or they say it's cheating with the Tama's life.
Either way, Debugging is actually a test program that BanDai uses to make sure each character is included in the v-pet and that they all have their proper animations.
UnDebugging is when you erase the pencil marks you made before.
