Are you getting just a Tamagotchi Friends? Or the new Tamagotchi Friends: Dream Town?
If your getting the Tamagotchi Friends, beware of the perfect care character curse! By curse, I mean that you'll only end up always getting Mametchi/Cofferetchi if you give it perfect care. But perfect care isn't a bad thing, it only avoids you getting other characters like Pianitchi.
But I know a solution to that..
Here's how you can get bad care characters:
Fill it's hunger by 1 heart, and wait at least an hour until it beeps.
DO NOT FEED IT UNTIL IT DOES NOT BEEP ANYMORE
And filling it's Happy up won't affect anything.
Then after it doesn't call for attention, feed it once and then repeat.
Now all you have to do is wait for it to evolve into Adult stage, and it won't evolve into Mametchi/Cofferetchi!
Then you have to feed it like you regularly would.
Hope this helps if you want to not only get Mametchi/CofferetchI!