It's a rat-like tail, actually - hairless, flexible, tapered at the tip, the same color as the rest of his skin. Hence the comment about Ganesh, whose traditional mount is a rat. The symbolism is the overcoming of obstacles.

This House has a good life here, and since his Wilson left the way he was supposed to, now that he's got a finalized sense of closure he's going to stay. But that wouldn't preclude him from being the occasional tourist.