As your pets grow up, they change into new and exciting evolutions. Pakka Pets hatch from eggs into babies and eventually evolve into children, teens and finally adults. How your Pakkas evolve will be entirely based on the care you've given them. You can get a new Pakka Pet every time you play. Everything from the love you give your pet, your Pakka's diet, sleep schedule, and experiences play a role in determining which Pakka Pet they will become. Figuring out how to get each evolution will be a puzzle in itself!
Basics of Evolution
A Pakka Pet evolves when his Evolution Meter, on the stats screen, fills up completely. Different characteristics lead to different pets, and you can track your progress using the Magnifying Glass item: it will show you the evolution your pet will reach if you keep treating him the way you have, whether if it's a new discovery or not, and what can be done better. This last part is very important, as it tells you what to fix to get a different evolution!
This is done in two steps; if you use the Magnifying Glass when your pet has recently evolved, it will tell you to fix his happiness and hunger. To fix that just make sure to have all his empty spots filled up (you'll know when you're done when your pet sparkles after finishing their meal; however, if instead of sparkles flowers appear, that means the other meter needs another meal or snack to completely fill it up.)
If you use the Magnifying Glass again, it'll show you a different evolution and new requisites for the next one: Weight and Discipline. The only ways to make your pet thinner are either buying a Weight Loss Potion, or feeding it non-fat meals and waiting. Playing in the Theater or exploring the mines don't seem to have an effect on their weight, nor does making them run on your house following your finger. As for discipline, it's easiest to find food your Pakka Pet won't like (such as Broccoli), try feeding it to them so they get picky, then dragging them back over to it.
A Pakka Pet won't evolve with the lights turned off. However, if the bar is filled up and the Doctor says it's about to evolve, you won't be able to change the evolution. It's pretty neat to keep your pet in a specific age for a while!