Released: 2008, Wii
Mario Kart Wii was the anticipated follow-up to Mario Kart DS, where it took the series in a fresher direction by introducing various elements that went on to further define the series. One notable feature was online play, which thrived all the way to it's eventual discontinuation which still manages to be strong in the homebrew community.
Despite it's relatively smooth development, the game has a surprising amount of leftovers tucked away within the surface. There are many earlier models of characters and karts, unused object animations, and a lot of hidden graphical details showing points from various stages in the game's development!