i really like this game so far! there appears to be a few glitches here and there, e.g. sometimes my pet won't go into one of the areas but will come back in the next one. overall though, very good game, i love the music and it's really well done :)
Passive or hurt pets stay away from enemies- kill all the enemies and/or have a heart drop on the screen somewhere, and your pet will return- assuming it's Active via the whistle.