CTR: Crash Team Racing - Story
From the depths of outer space, a large alien ship approaches Earth. Its pilot introduces himself as Nitros Oxide, and he claims to be the fastest racer in the galaxy. Oxide explains that he likes to challenge racers from different planets, and he forces their inhabitants to play a "game": the crabby alien will be racing against the planet's fastest driver, and if he loses, he'll leave the planet alone. However, should Oxide win, he'll turn the Earth into a gigantic concrete parking lot and turn everyone into his slaves.
Left with no choice, Crash and his friends decide to hold a racing championship and determine who's the fastest racer to take on Oxide. Even Cortex gets in on the action, since conquering the planet has been his goal long before Oxide came along. And so, the racers begin working on their karts and honing their skills to save the planet (and perhaps enjoy a bit of fame in the process).