Crash Twinsanity - The Bug Run
Another prototype uncovered by Jon Burton, this one contains quite a bit more content and a few updates compared to the December 2003 build. You'll notice, for example, that even though the HUD still has words instead of icons, the font is now a faithful recreation of the same one used in the original PlayStation era, as opposed to the entirely new one used in the final version. The E3 2004 demo uses this same classic font, so it was replaced fairly late during development.
Additionally, an entirely removed area can be found in this prototype. See, in Jungle Bungle, there's a seemingly redundant picture of a tribesman bouncing off a worm just before Cortex teaches you how to do it. The picture is there because this path used to have a divergence on the left, with a second picture indicating what you could expect there (as seen above).
The Bug Run, as it was internally nicknamed by the developers, was an optional route where Crash would go underground and be chased by a myriad of bugs in a typical scene where you'd run towards the camera. This should sound familiar if you've played the level Classroom Chaos, since the bugs were eventually moved to Cortex's part of that level. The reason this segment was cut is because it was much too difficult.
Jon Burton, founder of Traveller's Tales, has posted a video of this section as found in a prototype. This particular prototype doesn't actually feature the bugs themselves or even a fixed camera angle, but it gives us a good idea of what it would have been like.