Debugging is when you can choose the character you want from a list (that list even includes rare characters!) But watch out; you can permanetly destroy your tama if you don't do it properly.
Here are step by step instructions on how to debug (I've never done it before, although I know how).
1) Go to the back of your tama and unscrew the big screw
2) Take the back off and the battery out
3) Get a smaller screwdriver and unscrew the four little screws
4) This is where it gets tricky. Do you see the two little semicircles that sit right below the word debug? Good. Now take a dull pencil and rub the semicircles together in a horizontal motion. DO NOT press too hard!!
5) Blow the graphite from the pencil out of the debug circles (Try not to touch them)
6) Fold the back of the tama back over and put the four little screws back in
7) Put the battery back in
8) At this point, it should beep. If it doesn't, you either had the sound off or it didn't work (and may have even damaged your tama). If it has pictures on the screen, it's working (and if it didn't beep, you have the sound off or it's broken). Now put the back on and screw in the big screw
9) Flip through the characters with button A until you find one you want. Then press button B to select.
I hope I helped with anu debugging confusion.