There are 5 unused\cut levels inside the Beta of Crash Bandicoot Beta.
ASTOUND THE SKUNK
The first is the "Cliff Level", called by the Crash fans "Astound the Skunk", it's set in a cliff where Crash has to walk backwards like in a boulder level and then must descend along the cliff. There are unseen and unused features, like the skunks that can use a farting attack never used in the final version, there are unused dingo enemies that weren't programmed, so that doesn't hurt Crash, there are also sliding rocks and wood axes that collapses when Crash walks on these, like in Crash bandicoot 2. There's a weird bug that makes crash green in some parts of the level, the level is almost completed, there are no boxes and no warp pads at the end of the level. The background is unseen and unused in the final version, it shows the other two islands from a different view. It is an easy level, probabilly it should have been set before the Papu Papu boss stage.
Is the famous "Waterfall Level", it's set in a river but crash has to climb a great waterfall and avoid obstacles. The first part of the level shows a part that hasn't got textures, but everything else is textured. There are the unused dingo enemies, the skunks, there are no boxes and there are new features unused in the final version: flowers used for jumping, wood springboard actived by sliding rocks and turning platforms-like-mill.There's no warp pad at the end but it seems that in some versions of the beta crash at the end should be warped in Toxic Waste.
It's the "Cave Level". It's an unfinished level already textured but cut near the beginning. Crash starts the level by landing from a well, this is a mysterious entrance never seen and never used again. The setting is really similar to the stage Cavern Catastrophe in Crash Twinsanity, with acid pools, huge crystals and totems. The walls hurt Crash for unknown reasons, the acid doesn't hurt crash, there are no boxes and the level is uncomplete.
This stage is known in the web as the "minigame", but it is an incorrect attribution as actually this level was used for testing the spiders and the scientist that throws potions, there are TNT boxes and three wood boxes with inside three tawna powerups that leads you in a bonus round. There is also a hill were crash turnes green, like in the cliff level. There were hundreds of these test levels, but all were removed except this one that was hidden in the beta, probably it's the last test level.
This level actually is fully playable in the beta but was cut in the final release because the level was too difficult. However, another theory argues that the name "Stormy Ascent" was already used in another game by a rival developer company and their game was about to come out at the same time Crash was about to ship so they had to cut the level. In any case Naughty Dog preferred to cut it as it wasn't enough tested. The level is a twisted version of Slippery Climb, it's the most difficult level ever in the crash games, there are the platforms of The Lost City that drop off crash if he lands on it, the eagles sometimes fly horizontally and not vertically and the platforms are faster than ever. Even one of the creators of crash bandicoot said that the level was too difficult. Anyway the level was left inside the final version and it can be played throught cheat devices, its gem has a white colour and it doesn't affect the percentage of completing of the game.
Naughty dog creators said they planned to insert another level in Crash, this level had to be setted in a cave surrounded by magma, this stage should have been similar to the Koala Kong stage but it was immediately removed due to graphical glitches because the Playstatio One didn't supported the graphical data of the magma. Anyway the magma was inserted in the Koala kong stage and it has no graphical glitches. This level should have been set before the Koala Kong Level.
All these levels exept Stormy Ascent were removed due to lack of time or graphical glitches, instead of these five levels were inserted the levels "Whole Hog" and "The Great Hall".