Bunnies are currently the only completely friendly creature type and there are only two of them. Maybe a bird creature that's similar in size to the bunnies, and instead of healing like the bunnies do they could provide some sort of temporary boost. They could fly around then land and begin doing a mating dance when Liam gets close.  Adding a few bunnies and birds around would populate areas with more than just the designated creatures without adding new obstacles.