First things first, I would like to say that I searched for an actual decent topic covering all this stuff, and most of what I found either devolved into a topic about something else entirely, or just didn't cover all of the bases.
Thanks to the guys over at Unseen 64, a lot of the info that has been collected over the years has been put into one long article. Unfortunately, because it was translated from Italian, the translations are a bit awkward as a result. Here is the article, for those that aren't familiar with it.
http://www.unseen64.net/articles/zelda64-project-development/
The purpose of this topic is not to re-do what monokoma and others did over at Unseen 64, but to come up with something a little more coherent, and focused (no offense to those guys, of course), with an emphasis on the "true" Ura-Zelda and Gaiden when it was being developed for the 64DD, and less of an emphasis on "Beta quests" (Though some of the stuff featured in those "quests" is probably linked to the 64DD connectivity that the original cartridge version of OoT had, so I suppose it's still relevant to the discussion).
I would like to separate the facts from the fiction, and discuss a couple of things. I figured instead of going to a Zelda forum (which may be over saturated with kids who couldn't care less about this stuff), I figured I'd ask the diehards over here instead.
1) How much is really known about the Mario Artist:Talent Studio/ GB Camera/Capture Cartridge connectivity with Ura Zelda and/or Zelda Gaiden? Was this only discussed in passing by Miyamoto-san and co., or is there evidence of more "mask" related stuff in OoT/MM's code?
I did find this in an older topic, that does shed some light on it.
Maybe a lot of those masks had originally been intended for the DD version of Majora's Mask, when it was still under the "Gaiden" name. It sounds like Ura was going to include masks, and it's probably safe to assume that the emphasis on masks in Majora was something that was lifted from Ura-Zelda.
Nintendomad said:
Yes Master Quest was a part of the 64DD game, but after clearing all thew dungeons, more dungeons opened, as well as extra battles. The game was planned to have some sort of randnet connectivity too, which says to me that a boss rush, or something similar would be in practice, as well as the known fact that the disk would be compatible with the mario artist titles, and also include mask games that were present in Majora no Kamen.
2) I know that Zelda Gaiden/MM would have utilized the internal clock of the 64DD (which would have included a lot of the features intended for Zelda 64) and was originally slated to last 7 days instead of 3, (as well as add a new fishing mini-game), but were their any other (known) features that were scrapped that didn't make the cut to cartridge? Were dungeons really left unfinished/removed, or is that just speculation?
3) Is it safe to assume a lot of the things that would have been in the 64DD version of Ura Zelda, ended up in Majora's Mask? (Since we all know that Master Quest is a poor man's Ura-Zelda, and didn't really "add" much of anything)?
Early on, Miyamoto made it sound like Ura-Zelda would have in fact had new content in "similar environments", but then later seemed to go back on that, which is why I have a theory that a lot of the Ura stuff ended up in MM. I'm not sure if it's just a rough translation of Japanese to Italian, and then to English, but Miyamoto was quoted as saying
“you first play the initial disk version of Zelda — after finishing everything, you can enter into the world, into the basic design of the same."
If that's anything close to what he said, it probably means that Ura was (at that point in development) planned to be something very much like the Master Quest which we ultimately got, but had originally been planned to add new content to Ocarina of Time. This new content was later absorbed into Zelda Gaiden on the 64DD, which quickly evolved into the cart version of Majora's Mask, losing a lot of planned features in the process..again..
I've looked at the debug threads as well, and it sounds like nothing major (like say, the Unicorn Fountain) has been found in the code for OoT, MQ, or MM. It's definitely interesting to see so much beta stuff pop up after all of these years, but it's doubtful much of that was considered for Ura, with some of it being as old as it is (I'm mainly referring to stuff seen in screens/videos from '96/'97).
Sorry for such a massive post! I look forward to hearing from other diehard Zelda OoT/MM enthusiasts, and N64/DD fans a like.