List of Mario Kart: Double Dash!! pre-release and unused content
From the Super Mario Wiki
This is a list of pre-release and unused content for the game Mario Kart: Double Dash!!
The models of the characters are from Super Smash Bros. Melee, and Mario and Luigi are seen in this trailer of a very early build of the game, driving separately, each in a simple, blue kart. It was originally called Mario Kart for Nintendo GameCube, and it is likely that this early build of Mario Kart: Double Dash!! was overhauled for the final game, as it resembles nothing like it.
Several screenshots released during the development of the actual Double Dash!! build shows different textures, tracks, speedometer HUD, and racer mugshots.
Time trial code
Pressing at the end of a trial mode race (where save ghost and replay are) will bring up a series of numbers and letters, a code that stores the race time, lap time, characters used, kart used and course I.D. This was used for a Japanese contest.
Some unused data has exists in a Double Dash!! demo from Interactive Multi-Game Demo Disc Version 13.
An icon and trophies for a Reverse Cup have been found, which possibly could mean that a cup where the racers drive the tracks backwards was planned. In addition, early character icons have been found featuring Donkey Kong Jr. instead of Diddy Kong.
Early Sherbet Land Course
Hidden in the European Demo Disc 10 demo is an early version of Sherbet Land. The name of the course is Dekoboko. Inside the objects folder includes a Wiggler Wagon, a Mario tree, an early version of Freezie, and a sign.