I had to save the creepiest for last, since today is Halloween and all.
It’s Dry Bones, the zombie/skeleton Koopa Troopa. These little creeps debuted in Super Mario Bros. 3, and then immediately re-appeared in Super Mario World, cementing their inclusion in Mario canon.
I always thought they were a cool idea, but when Dry Bones became a playable character in Mario Kart DS, that’s when I was definitely on board with them as a concept, and they’ve been one of my favorite Mario enemies ever since.
Happy Halloween, everyone!