Shell Cup

The Shell Cup is a representation of four cups introduced in Mario Kart DS, each of which consists of four races taken from the previous Mario Kart games. Shell Cup's symbol is a Green Shell and it features tracks from previous Mushroom Cups and Flower Cups. The tracks are usually quick and simple with little hazards. It is the first of the four Retro Cups. The cup's length and difficulty is on par with the Mushroom Cup.

Mario Tennis Open
The Shell Cup also appears in Mario Tennis Open as the third cup in the Star Open tournament series, but the shell is a Red Shell instead of the usual green. The trophy is designed as a Red Shell on top of a tower that resembles a feature from Bowser's Castle. This cup is held in the Bowser's Castle court, with the matches having three sets for the starting round, three sets for the semifinals, and five sets for the finals.

Trading Card info
"The first of four Retro Cups, the Shell Cup is made up of four great blasts from the past. One track from GameCube, one from DS, one from Super NES, and one from N64. It's a great mix, and they all get a face lift with the graphics boost in Mario Kart Wii."