There's an unused course in a demo of Mario Kart: Double Dash!! that is only available on the PAL November 2003 demo disc. To extract the TGC file, you will need the TGC2GCM Converter to convert them to GCM. This what appears to be an early version of Sherbet Land, and the course name is Dekoboko. The objects folder includes a Wiggler Bus, a Mario tree, an early version of Freezie, and a sign. Since there isn't a way to load the model in game because the course model doesn't work when replacing the final version of Sherbet Land. I did get the Freezie model and the early skybox to work. https://tcrf.net/Proto:Mario_Kart:_Double_Dash!!/European_Demo_Disc_10_Demo
Woah, very cool. MKD!! is my favorite MK game and one of my favorite games ever. Thanks for sharing this! I'd love to be able to play the unused level.