There is a persistent rumor that N. Oxide was intended to be a playable character, unlocked through completing various tasks and beating certain records in the game. Although he can be selected using a cheat device, he is extremely buggy, and will most likely crash the game. According to the developers, they once considered making him a playable character, but were unable to due to the extremely limited memory of the Playstation, and his boss level was designed with those limitations in mind in order to make him functional.
Contributed by CosmykTheDolfyn