Lead designer Paul Gardner and artist Daniel Tonkin explained that Cortex was made playable as an opportunity to explore his character, and was teamed up with Crash because "it didn't make sense to make them two opposing characters who were playable because the player would be kind of playing against himself". Producer and creative director David Robinson cited Jay and Silent Bob and "The Ren & Stimpy Show" as the central influences on the game's character dynamic, as both properties provide a variation of two opposing personalities spending a large amount of time together; "Ren & Stimpy" crew member Jordan Reichek wrote the game's script, provided creative input on the characters and game mechanics, and illustrated the game's cover art. The character Nina Cortex was created and designed by Duke Mighten for an early version of "Crash Nitro Kart", and was re-appropriated for "Crash Twinsanity" due to her popularity among the development team. Gardner created a rough model of Nina modified from that of Neo Cortex, and her final model was created by Chris Abedelmassieh. Nina's model was created over the course of a single weekend. Although "Crash Twinsanity" was intended to be Nina's debut appearance, Gardner was alerted to her early appearance in "" by Webb, who came across Nina's image in newly released screenshots of the game. Crunch Bandicoot was included in a cameo appearance due to his fan-favourite status. A stage taking place in Coco's mind, "Gone a Bit Coco", was removed because production was too far along to guarantee that the stage could be finished and played without crashing. Other content, such as a cameo by Fake Crash and the appearance of a good version of Cortex, was also removed, but appears in unlockable concept images in the final game. A punching maneuver by Crash that appeared in the "Crash Bandicoot Unlimited" demo was removed due to its inadvertent capability of destroying scenery. Rusty Walrus, a blue walrus character who pursues Crash in one level, was inspired by the final boss in the 1988 arcade game "The NewZealand Story".