TLM: The theory that UFOs are time traveler humans from 1000s and 1000s of years in the future.
and in this future time, humans have colonized all over the universe.
They come back to study us, mostly. Sometimes they step in and help, or hinder, depending on the situation.
The alien appearance is actually their space/survival suit.
In The Last Mimsy, they need fresh DNA because in the future humans are dying from a whole bunch of different reasons,
(mostly pollution and other 'human error' factors) so they send the DNA harvesting Mimsy robot stuffed animal back in time through a time traveling 'bridge'.
The 2 kids find the Mimsy and the gadgets with it, and learn how to use it because the Mimsy can communicate only with the little girl,
and the kids end up saving the future of mankind.
The DNA was in the little girls tear when she cried hugging the bunny, and one of her tears fell into the Mimsy's bellybutton.
The original story was written back in the 1940s.
Really was a good movie, just played on TV a couple nights ago.
Anyway, I think UFOs are what they are, but all operated by extremely evolved humans/humanoids from the future.