Dry Bones is the dead version of Koopa Troopa. He is most likely a skeleton because he fell in lava because he only appears in Bowser Castle's in Super Mario Bros. games. But anyway, he has the same shape as Koopa Troopa, but is a white/ grayish color, due to all his bones. He wears white gloves and boots. Very fashionable, right? His shell is all pale and cracked up, and his torso is his rib cage. He also has sharp teeth, and instead of white, lively eyes, he has gaping black eyes with yellow pupils. Ohh, scary. Outside of the Mario Kart series, a variation called "Parabones" can be seen, it's a Dry Bones, but with wings, this variation only appears in 3D games, the normal and winged Dry Bones never appear in the same games besides Super Mario Maker. In the Super Mario Bros Games, when one stomps on one, they fall apart, only to resurrect and resume their stroll on a platform, however, a superstar can get rid of them for good.
While Dry Bones doesn't appear as a playable character in Mario Kart 8, Dry Bones appear as obstacles in Bone-Dry Dunes. Dry Bones (as a playable character) returns in Mario Kart 8 Deluxe and the Dry Bones are still there in Bone-Dry Dunes, it's like a paradox.