I'm just about to finish up a science fiction adventure story in which a Precursor-type alien robot plays an important concluding role. I'm taking the term "Precursor" from my recent play-through of Halo 4, though the idea of ancient alien civilizations that build great works throughout the universe is hardly unique to that game (in fact, the Halo universe boasts both Precursors and Forerunners). David Brin's Uplift trilogy and at least one of Iain M. Banks Culture novels (namely Matter) feature such civilizations; according to what my dad has told me, Larry Niven's Ringworld is this, and, according to my friend Bryan, John Ringo's Posleen War Series exhibits such elements also.
Humans have even created precursor myths that are traded in serious (if, for many looking from the outside in, farcical) discourse: that aliens built the Egyptian pyramids or Stonehenge. And that train of thought - from my story, to others' stories, to myths about world wonders - made me realize something that I will never be able to un-realize: that a great deal of science fiction is nigh tantamount to the "I'm not saying it was aliens, but it was aliens" meme.
I mean, okay, not exactly, insofar as science fiction authors who invoke precursors probably aren't as crazy as this dude. But think about it: there's an enormous body of sensawunda that's kind of exactly this meme. Y'know? "Hey man, in this story... aliens." And in that other story? Also aliens. Aliens aliens aliens. ALIENS.
Hey, it's all good. I love aliens. (Assuming they are not like the Posleen, which Bryan described to me as "crocodile-centaurs.) But now that I've made this connection... well, I basically despise the story I'm writing, and I'm probably going to burst out laughing any time I read a book or a story that worldbuilds by sticking random wonders into the universe and blaming it on aliens. ("I'm not saying it was aliens, but... canonical science fiction.")
Not that I don't love those stories, it's just going to be really, really, really difficult to get this image out of my head.