spotcat asked: If my opponent's Gideon (or any other legal permanent, really) is enchanted with Imprisoned in the Moon, and I then target that Gideon with Crumble to Dust, do I then get to go and exile all their other Gideons?

Yep.

This works, and is a little bit mean. But Crumble to Dust only cares that the targeted permanent is a nonbasic land. The types and supertypes of other cards with that name in the controller’s hand, graveyard, or library don’t matter at all, just the name.