I had a mindblowing revelation the other day concerning Super Mario Bros. 3; you know how when you kill enemies with hammers and such, their sprite flips over as they die? Well, for the longest time, I thought Thwomps had a unique sprite when you killed them. All this time, I thought the reddish ring around their top spike, combined with the already flipped eyes, were a sad-looking face. Nope, turns out that it's just another flipped sprite.
But look at the sprite here and tell me you didn't/don't see that as well:
Heck, I
know that's a flipped sprite now, and even still, when playing the game, I can't unsee that face.