Crash Bandicoot: The Wrath of Cortex
Crash Bandicoot: The Wrath of Cortex
There are three unused levels still present within the game; an Airship Level, an unfinished version of Fahrenheit Frenzy, and a Warp Room that was presented at E3 2001. Out of the three, the Airship level is the most finished.

The E3 Warp Room is an area containing 5 warp pads, all of which have no collision and will not warp the player anywhere. Interestingly, each warp pad has a hologram of their respective levels overlaid on the pads. This feature isn’t used anywhere in the final game.

The Airship level and the E3 Warp Room can be accessed through Action Replay codes on the North American GameCube versions.
Contributed by ShyanVixen
The original PlayStation 2 version of the game had long load times that averaged around 47 seconds. According to the founder of Traveler's Tales, this was a consequence of a small mini-game intended to be incorporated during development.

Originally, you could move Crash through hyperspace during his falling animation and collect Wumpa Fruit. Any Wumpa Fruit collected would be added to your totals when the level loaded.

Due to a fraudulent patent Namco had over loading screen mini-games beginning with Tekken's PlayStation port, it had to be removed. However, time constraints meant Traveler's Tales could not fix these loading times before release. The Greatest Hits re-release shrunk the loading times down to a mere 17 seconds.
Contributed by Regen-33
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The XBox and Gamecube versions of the game have an unused static Traveller's Tales logo, which is different to the 3D one used in the intro.
Contributed by psyducklover13
There are unused icons in the GameCube version featuring Mario, Luigi, Shy Guy and Yoshi from the Mario game series.
Contributed by psyducklover13
Most likely due to the criticisms of the long loading times in the first release, The Wrath of Cortex's Platinum/Greatest Hits re-release had shortened loading times.
Contributed by SpaceChimp
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During development it would appear that in part of the level "Crash & Burn", Crash would have had to save Coco from a hanging cage. Even though this task was removed from the final game, the cage is still present in the finished level, although Coco was replaced with a skeleton.
Contributed by SpaceChimp
While a lot isn't known about Mark Cerny's vision for this game, an animated video representing the proposed gameplay was made. Even though this is from long before the actual development began, the level in this video does strongly resemble the level "Crash and Burn".
Contributed by SpaceChimp
The game actually started out under the direction of Mark Cerny (producer of the past games) exclusively for the PlayStation 2 and was initially intended to be an open world adventure. After Universal Interactive (the holder of the IP) decided to take the series multi-platform, and have Traveller's Tales develop it, the decision was made to use the more traditional linear path level design.
Contributed by SpaceChimp
If you start a new file with the name "WOMBAT" you will get an immediate 106% completion rating. This is a reference to Crash's name before they named him Crash, aka Willie the Wombat. This does not work on the PS2 version of the game.
Contributed by Ripper Roo