How many pets are there in Mists and is there a limit?

Solution 1:

The number of pets has indeed exploded with Mists of Pandaria and the introduction of pet battles. There is still a limit because there is still a finite list of pets added to the game, ie. there is no dynamic generation of pets, all the new ones are in-game as critters/etc. I can't find a number easily in game despite the new interface which lists all pets including the ones you don't have yet, however Wowhead has the number pegged at 662 and there are achievements all the way to 400 pets collected currently in game.

Solution 2:

As Matthew says, 662 pets is most likely correct for the total number of pets in Mists of Pandaria.

However it looks like there is a limit on the number of pets - specifically you will be limited to 500, as captured on the beta, so you can no longer capture every pet in the game.