Let's see if I remember this right.
Back when Sonic Adventure 2 was still current, and Dreamcast games still had online support, Sonic Team had a contest where you could submit a design for a character/racing vehicle and the shape of the track that it would race on. The winning entry would be made 3D and
offered as a downloadable, playable add-on to the racing minigame in SA2.

My entry was supposed to be Nack/Fang, racing in that spiffy... thing. The track was supposed to be shaped like a pistol. Unfortunately, I don't think I ever actually submitted my entry for some reason. The winner was something involving an Eggbot character.