Check your tamagotchi against the checklist provided on that site.
I've managed to purchace two fake tamagotchis. Entirely my fault, the packaging says BanDai nowhere!
They looked like the pink and blue pair a little down
this page.
BUT MINE ARE FAKE!
They don't have the same stats display, they're larger on the screen than the real ones, have no number on the back, but apart from a few differences they're practically identical.
Oh well, i'm gonna keep mine just for the fun of it, but I will be getting a REAL BanDai Tamagotchi ASAP!