A long time ago, in a galaxy far, far away, I worked with some guys who put together an incredible proposal to ICANN for a new .geo TLD: http://www.ai.sri.com/dotgeo/ The proposal was not accepted, but .aero and .museum were, and we all now how those have since utterly revolutionized the internet.
Neat! Speaking of galaxy far, far away, the executive summary only mentions other planets in passing. I couldn't quite grok from scanning how you might access cells from the moon with this TLD. .aero may be questionable, but surely the boundless usefulness of .ninja or .moe isn't in dispute?
Full list of proposals that year here: http://archive.icann.org/en/tlds/app-index.htm