Its a glitch in your tamagotchi were you open up your tamagotchi and rub this button with a pencil. You'll then be able to choose the character you want. This is the basic procedure.
1. Use a small screwdriver and take out the back of your tamagotchi.
2. Take the battery of your tamagotchi.
3. Take a smaller screwdriver and unscrew the four small screws in the battery compartment.
4. Find the circular thingy under the word debugged in the inside.
5. Take a pencil and VERY CAREFULLY rub the circular thing.
6. Screw everything back together and put the battery back.
7. Pick the tamagotchi you want and enjoy!
WARNING: 20% chance tamagotchi will bust. Reconsider if your clumsy or afraid of your tamagotchi breaking.
Hope this helped. Uilleam