PC | Submitted by PraveenAge up your pet
Put your pet in the care center and go and change the Date/time Properties If suppose the time is 1300 on Jan 8th 2000 change it to 1300 10th 2000. Do the same every day and your pet will be adult in just 9 days..
GBA | Submitted by GamesRadarSecret character
Raise a tamagotchi on carrots only and see it evolve to a Mimitchi