Following the release of The Wrath of Cortex, Traveller's Tales begun working on a new racing game that served as a sequel to Crash Team Racing. Partway during development, Universal Interactive handed the game over to Vicarious Visions (which eventually became the Crash Nitro Kart we know today).
Traveller's Tales's original vision remains mostly shrouded in mystery, but there is a lone piece of concept art that reveals something quite interesting:
This game would have been Nina Cortex's debut in the series. When the shift between studios occurred, Traveller's Tales kept the design so they could introduce her in Crash Twinsanity instead. Ironically, Vicarious Visions ended up being responsible for her debut anyway, as prior to Twinsanity's release, she was placed in their new game, Crash Bandicoot Purple (a.k.a. Crash Fusion), without Traveller's Tales's knowledge.
Another thing to note about the concept shown above is that the kart design is quite different from those used in the final version of the game.
Kudos to Paul Gardner and the author of the image for the concept art and this information.