Tenth Dimension

The Tenth Dimension is the moral opposite of Crash's home dimension. Everything that is considered benevolent in Crash's dimension is malevolent in the Tenth Dimension and vice-versa whereas Crash's dimension is bright and colorful, the Tenth Dimension is dark and gloomy. The Tenth Dimensional equivalent of the luscious N. Sanity Island is the barren Twinsanity Island, where the feral and ferocious Evil Crash resides.

History
As a child, Dr. Cortex accidentally sent his pet parrots Victor and Moritz to the Tenth Dimension while testing his prototype Evolvo-Ray. Victor claimed that the severe "reverso-radiation" in the Tenth Dimension sharpened the skills of the parrots and warped their "fragile, egg-shelled minds", causing them to become the Evil Twins. In an earlier version of the game, this reverso-radiation would affect Crash and Cortex upon entering the Tenth Dimension, causing their personalities to switch. This would lead to a reversal of the Doc Amok levels seen earlier in the game (named "Mock-A-Doc"), in which Crash, who has taken on the form of Evil Crash, must attack Cortex and make him as angry as possible.

Trivia

 * In the cutscene prior to entering the tenth dimension, Cortex breaks the fourth wall and says "We were supposed to visit two dimensions, but we ran out of time.". This is a mocking joke on the game's development, as Traveller's Tales originally planned to include two extra dimensions in the game, but this idea was cut due to development deadlines and time issues for the game.
 * The tenth dimension used to look a lot different with some unseen things. There used to be an erupting volcano in the back and the sky was filled with clouds. This was an earlier version of the tenth dimension before the game's release.
 * The Tenth Dimension is stated to be between the 9th Dimension and the 11th Dimension. Nothing more is known about these dimensions.