Star Thwomp

Super Thwomps are a shiny variety version of Thwomps that appear only in the Mario Kart series.

Super Mario Kart
Super Thwomps first appear in Super Mario Kart on Rainbow Road where they act like regular Thwomps, though these Thwomps glow and spin racers out if they run into them, unlike normal Thwomps.

Mario Kart 7
Super Thwomps reappear in Mario Kart 7 (marking their first appearance in 19 years), with the return of SNES Rainbow Road as a retro track. Like before they behave like normal Thwomps, but using their modern spiked appearance from New Super Mario Bros. Wii rather than the blunt one used by the Thwomps on Bowser's Castle. Once again, racers flip if they run into them. They also cause the track to wave when they slam the ground, allowing racers to use them for tricks.

Mario Kart 8 / Mario Kart 8 Deluxe
Super Thwomps appear once more in Mario Kart 8, once again on SNES Rainbow Road included in the first downloadable content pack. Unlike Mario Kart 7, they use the same appearance as the Thwomps in Thwomp Ruins, based upon their Super Mario Galaxy appearance, though they still flip racers on contact. Along with the SNES Rainbow Road course, Super Thwomps reappear in Mario Kart 8 Deluxe as part of the game's base content.