In the same vein as using Skitter’s power on changelings or breezies, I wonder if/how Bitch’s power would work if she directed it at MLP timberwolves, which are wolves, but are made of wood.

I’m leaning towards the conclusion that it wouldn’t work because Worm operates more with physical magic than idea-based magic. MLP’s timberwolves reflect the idea of a wolf, but not their biology. I think that would be the case with most powers affecting wolves, but Bitch’s power in particular is highly dependent on wolf biology to make the transformation happen. What would her power even do to make wolves made of wood into hellhounds?
Now, her power working on these guys is way more plausible:


Though I don’t think Cerberus particularly needs it.