UFO's are Nazis from inside the Earth
So this settles it -- UFO's are really super-intelligent Nazis that escaped WWII and now live inside the Earth. (Which is hollow, by the way.) Glad that little riddle has been solved!
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And here I thought that the Earth was filled with melty iron and rock, that Nazis were all dead (not counting the NEO's), and that UFO's were airplanes and blinky lights. WTF was I thinking?!