This one came to me in a dream last night.

Aliens arrive on Earth, open “ambassadorships” which are basically schools where the aliens teach their philosophy of universal peace and understanding. At the final level of training, then turn an ecophage on the person, rendering them into the ubiquitous gray goo that in turn does give everyone universal peace and understanding, since we’re all just one massive slop pile of nanites. Of course, some one finds out, and a Scientology/Logan’s Run-esque narrative happens.

Second came to me today on the way to work.

A man builds a vat of nanite disassemblers. You throw in trash, they spit out the raw materials you used to make that trash. The disassembler swarm is borderline conscious, so that they can learn to do a better job, and enjoy doing that job. People are scared that this borderline intelligence is a threat, that somehow it’ll want more and escape into the world. Upset, the man asks the swarm if it happy or if it ever felt trapped. The swarm, suddenly now aware that there are options, escapes the take and spreads out into the world. It’s a fable parable; don’t ask questions you don’t want answers to.