The following comes from a Reddit AMA with dev Dylan Cuthbert...
On the cancellation of StarFox 2 and the leaked ROM:
I think it was a shame but understandable given the time frame - the PlayStation had just come out and the 3d tech in StarFox 2 was showing its age. The leaked roms didn't have the "rogue" style randomization of events, so every time you play you get a new adventure/different sequence of events.
On a mishap with early documents detailing the N64:
I remember one from my Nintendo days where Giles (fellow coder on StarFox) and I had been drinking with the Nintendo staff, this was towards the end of StarFox 2 and Giles had just got the loose leaf documentation (several hundred pages) for the very early prototype of the N64... anyway, I didn't have my bicycle so I hitched a lift on the back of Giles' (it had two metal pegs attached to the back wheel that you could stand on, and this kind of "double riding" was often seen in Japan in the 80s and 90s) ... anyway, we get back to town and we're crossing a busy road when Giles hits a pothole or something and we go flying, but so do the 100s of loose leaf pages, all over the road in central Kyoto... and the walk light blinked to red so we were laughing our heads off, completely drunk, frantically scrambling around picking up all this top secret documentation, jamming up the traffic. It took a while :)
Cut content in the original StarFox:
I think that everything we experimented with got put in apart from the very early free range mode experiments that got scrapped. (We had a massive tank that shot off tons of missiles at you)
Opinion on StarFox Zero:
I think platinum did the best with what they were given. That franchise is very difficult to work on and innovate with because people expect/want it to be better than their nostalgia for the game and that's a tall order. The walker mode was close to what we had in the original but of course no one had made a 3D platformer at that point so the StarFox 2 controls are a little odd. Nowadays there are common mappings and better game camera paradigms. A lot of the platform experiments we did were taken directly into Mario 64 by Miyamoto.
Thanks to CM30 for the heads up!