Apparently it is necessary to interact with the owls in order to solve the puzzle in the owl statue room. Is it possible to interact with the other creatures, such as snails and crows at any stage in the game?
From what I've seen (in New Game+ now), No. Dont' really have a definitive answer, but I'm guessing it doesn't change. I'd like to kick one of those cute spinning turtles though.– Doozer BlakeApr 24, 2012 at 12:53
Not sure if it counts, but there is an invisible ghost who says things in one of the rainy world levels too.– jamesdlinApr 25, 2012 at 3:47
There is more than one Ghost that talks. At least two possibly more. I can't find a definitive list... off to question.– EBongoMay 1, 2012 at 0:22
No, none where they talk or react back like the owls. If you run near the other perched birds, though, they'll fly away. And the turtles run toward you only to spin away when you come near.
If you jump on some land creatures (Rabbits possibly?) they die and vanish; the turtles flash for a bit (mario tribute I believe).