We welcome all sorts of creative expression of our works! The only specific thing is with fanfic neither of us will read it (it's typical etiquette), and our own personal interaction with fanworks may be limited. For monetary fanworks, one-off commissions are absolutely fine, but more mass-produced merch is discouraged (not that there's really any real push for that, at least right now).

With me personally, I believe in a polite separation between creator and fandom. A story is for fans to enjoy with other fans, and a creator's role should be minimal in fan spaces. In general though, how fans of our characters express themselves is something amazing and flattering. By all means the greatest compliment in the world, that!