In elementary school, a couple friends and I sketched out an entire game's worth of ideas for Mega Man bosses and mailed them to Capcom (this would have been 1990 or so). I remember how thick the envelope was.

I recall their response being very human, warm and encouraging, but it also included all of our original sketches, with a very direct (but kid-understandable) statement that they were obligated to return the originals to make it very clear that they were not kept and thus could not possibly be understood to be "inspiration" for anything that might be in a future game.