Weird games don't just come from Japan. Europeans have their fair share of them, but they're mostly for '80s computers like the ZX Spectrum and the Commodore 64. Internet commedian Stuart Ashen assembled this video highlighting a few Easter eggs found in games most of the world has probably never played.
I've always found hidden nudity in sprite art very funny. Not because "oh tee-hee that's a naked person," but because someone spent a great deal of time trying to shape that image and probably an even longer time burying it beneath other graphics. At that point, why include a naked woman in your game at all?