Diddy Kong Racing Adventure is a rejected pitch made by the Climax Group for a Diddy Kong Racing sequel on the Nintendo GameCube around 2004. The project was never announced to the public in any capacity and only became known after an amateur video game archivist acquired the prototype and published a video about it in November 2016. Only the demo for their pitch was developed, in around April 2004, running on Xbox hardware as the tools had already been developed at the time.

After his defeat in Diddy Kong Racing, Wizpig allies himself with the Kremlings to get his revenge. While Diddy Kong is away on a visit to Timber Island, the Kremlings have been kidnapping members of the Kong clan, while Wizpig is in the process of converting Kongo Island into a gigantic raceway. Upon returning and seeing the Kremlings bulldoze the forest, Diddy Kong gathers the racers of the original Diddy Kong Racing to challenge Wizpig and stop his destruction of Kongo Island.