The Legend of Zelda is coded into Doubutsu no Mori+ and Animal Crossing, but was never made available by any means.
Super Mario Bros. was given to players of Doubutsu No Mori+ as a Famitsu prize, but while the game exists in the Animal Crossing code, it was never actually made available.
Mario Bros. was only available to Animal Crossing players, through scanning e-Reader cards.
All three of those games, plus Ice Climber, were removed from Doubutsu no Mori e+ as furniture items, though with hacking it's possible to use both Mario games and Ice Climber with Advance Play.
There were apparently plans to hold contests awarding exclusive items such as the "autumn medal", which would be awarded through the Nook code system, but as these contests never actually took place, the items can only be obtained through datamined codes.
The "DUMMY" item is a floating white triangle with "ダミー" (dummy) written on it is a test item that was clearly supposed to be dummied out, but for some reason, it's one of the possible prizes for winning a game with a villager camping out in an igloo.
Within the game's data is code for a cut sickle item. Not much about the item is known beyond a name and an icon that was found in data for the N64 version that was included with the 2020 Gigaleak, as hacking it back in and equipping it does nothing. Based on its name, one can infer that its use would be cutting smaller (i.e., excluding non-sapling trees) plants (e.g., weeds, flowers, or saplings). In the final game, digging them up is possible, so having two tools to get rid of weeds, flowers, or saplings would be redundant, especially since weeds can be removed more quickly without a tool (though since picking flowers wasn't possible until later games, digging up flowers is the only way to get rid of them) and dead saplings disappear the next day if they aren't dug up manually. Incidentally, dropping the sickle on the ground causes it to appear as a toolbox, which was only used to represent dropped tools in the N64 version before making a return in most sequels (with the sole exception of Animal Crossing: City Folk).
In addition to the various furniture items of specific NES games, there's a generic NES purchasable from Crazy Redd. It's not just decorative, though— the item contains fully-functional code to load and emulate NES games from the Memory Card. What's more, the N64 release has a dedicated menu for viewing and deleting NES ROMs from the Controller Pak, accessible by selecting the "Save a Letter" option at the Post Office while carrying ROM data. It seems that Nintendo planned to release additional NES games this way, in sort of a prototype of the Virtual Console, but nothing ever actually came of the idea.
The ROM-loading feature can also be used to patch Animal Crossing itself, implying that Nintendo may have planned to also use this function for Downloadable Content. Indeed, version 1.01 of Doubutsu no Mori e+ contains tags for the Famicom Disk System BIOS, Famicom Grand Prix, Wrecking Crew, Vs. Excitebike, Kaettekita Mario Bros., Dr. Mario, and Zelda II: The Adventure of Link. None of these are accessible in e+ or any other version of the game, indicating that Nintendo might've planned to patch them in via promotional events through the loader function.
When telling Tom Nook certain datamined item codes, he'll tell you that the resulting item was a reward for a contest. There's no record of any contest connected to this feature ever actually being held, but the system appears to embed the contest name in the item code, implying that there were plans to hold contests like this indefinitely.
Within the game's code is data for a female squirrel character named Shaki ("Crispy"). While commonly believed at first to have been a scrapped villager, further datamining revealed that she was actually intended to be a special character, specifically a travelling doctor (presumably for curing bee stings, which e+ would make possible through the new Medicine item, which would appear in all later installments).
Fan Translation: The original Japan-only N64 game has a mostly incomplete translation to English by a team of fans. As of April 2020, only text for crucial events, such as tutorials, is displayed in English, with most standard dialogue (especially that of villagers) remaining in Japanese. A translation for Doubutsu no Mori e+ is also in-progress, but it too is incomplete, owing in part to the presence of extra text not seen in Animal Crossing and the translator's desire to fix up more awkward gameplay elements like the dial-based typing system. Of note is that both fan translations simply recycle text from the official English release of Animal Crossing, so the incomplete state of them may be due to a combination of difficulties managing how text is coded in-game and the sheer amount of text that needs to be managed (the latter of which was also a major obstacle for the official localization back in the day).
Feelies: The GameCube versions came with a free 59-block memory card preloaded with special data that gives you two free NES games and includes Animal Crossing-themed stickers to decorate it with. It seemed like a fantastic deal— until you saved your game and discovered that one file takes up nearly the whole card by itselfnote if you include the data for things that are normally inaccessible, like the NES games, it really does take up the whole card.
The GameCube version didn't come out in Europe until 2004, presumably due to the sheer amount of text that needed to be localised across several languages.
The N64 version was released in China in 2006, five years after it did in Japan.
Marth Debuted in "Smash Bros.": Due to the lack of localization of the original N64 Dōbutsu no Mori, Tom Nook, Mr. Resetti, and K.K. Slider all made their first international appearance as trophies in Super Smash Bros. Melee. Interestingly, these trophies use their Japanese Animal Forest modelsnote Tom Nook has the "店" (mise, shop) kanji on his apron rather than a leaf, and Mr. Resetti is wearing a button-up shirt rather than his usual overalls even in the international versions, likely because the English release of Animal Crossing wouldn't be out for another year and their Western redesigns hadn't been finalized yet.
The original game, Dōbutsu no Mori for Nintendo 64, is Japanese-exclusive. The Gamecube Updated Re-release, Dōbutsu no Mori+, was released internationally as Animal Crossing (though heavily altered to the point of essentially being an entirely new game).
The third version, Dōbutsu no Mori e+ for the GameCube, only saw a release in Japan, and introduces several features that never appeared in the series again. One example is banging on the Nook's Cranny door with a shovel after closing, which allows the player to shop with a half-asleep Nook and inflated prices. However, a select few of its features (such as being able to join in on a conversation between two animal villagers) made their introduction to Western audiences in Wild World. Similarly, future games brought back several of the villagers themselves (and a handful of islanders too), with some being reintroduced in the vanilla version of New Leaf and others in the Welcome amiibo update. Many of the purchasable town decorations in e+ also made reappearances as Public Works Projects in New Leaf. The game was designed as an enhanced reverse-localization of Animal Crossing, and as such retains the broad majority of changes it introduced compared to the first two incarnations (including most of the Westernized character designs and the use of NES systems instead of Famicoms).
More like "refitted for re-release," but nevertheless true. In the early days of its development, Dōbutsu no Mori was planned to take advantage of the 64DD's internal clock in order to be able to run the game in real time. However, after the 64DD turned out to be a commercial failure, the project was shifted over to a standard N64 cartridge (which it was ultimately released on), leading the real-time clock to have to be operated by a battery-powered chip in the cartridge itself due to the standard N64 not having an internal clock of its own. The updated re-releases, meanwhile, were able to take advantage of the GameCube's own internal clock, thus fulfilling the original plan for the game's real-time clock feature. Since all of Nintendo's subsequent consoles have internal clocks of their own, this means the trope also carries over to the actual sequels as well.
Also being more of a case as "refitted for re-release," early content from Dōbutsu no Mori leaked as part of the 2020 Nintendo "Gigaleak" revealed that there were plans to feature Tortimer, Wisp, and the museum as early as the N64 installment, with early textures for the former two and Blathers being found among the leaked files (images of the textures applied to the GameCube versions' in-game models can be seen here). Ultimately, the three characters and the museum wouldn't debut until Dōbutsu no Mori+/Animal Crossing, implying that technical limitations with the N64 may have kept them out of the series until the GameCube re-releases came to fruition.
Also revealed from the Gigaleak was the idea of having Copper and Booker be human guard soldiers in the vein of the Grenadier Guards in England; while Copper and Booker would remain dogs for the entire series, the notion of them being Grenadier Guard parodies would be implemented in both Wild World and City Folk.
Remade for the Export: The GameCube game is an enhanced version of Dōbutsu no Mori+, the initial GameCube port of the Nintendo 64 original, and was the first game in the series to be released outside Japan. Much of the game, including its character models, furniture, and holidays, were reworked to have a less uniquely Japanese and more "international" feeling, as the localization team wished to give players outside of Japan the same experience worldwide. The original development team was so impressed that they imported these changes back into the Japanese version with Dōbutsu no Mori e+, adding even more new features atop of that.
Screwed by the Lawyers: Two paintings in the N64 release, the Dreadful Painting and the Novel Painting, were removed from the GameCube versions as a result of copyright issues. The source artworks, The Scream by Edvard Munch and Composition with Red, Yellow, and Blue by Piet Mondrian, were still legally owned by the artists' estates at the time, with the Munch Museum being particularly aggressive about enforcing that ownershipnote the entire lifetime portfolios of both Munch and Mondrian's works wouldn't enter the public domain until 2015. The two paintings were still in the code of Doubutsu no Mori + though and could be brought over from an N64 save file with the now-discontinued Data Moving Service, but were removed from the game's catalog and could not be donated to the Museum. In Animal Crossing and Doubutsu no Mori e+, the paintings are removed from the code as well, with their index numbers instead pointing to duplicates of the DUMMY placeholder furniture item.
Sequel First: The N64's Animal Forest never left Japan, while the GCN's Animal Crossing was the series's international debut. That said, the GCN game isn't exactly a "sequel" in the sense that the DS game is a sequel to the GCN game, and is closer to an enhanced port.
The Shelf of Movie Languishment: Katsuya Eguchi mentioned in a 2001 interview that the original Dōbutsu no Mori game was done and ready to go by March of that year, but instead it was delayed one month intentionally due to the Game Boy Advance's launch.
Technology Marches On: This game first released in 2001, and as such features technology from that era. Despite running in real time, technological advancement has been frozen in time.
Villagers will sometimes ask you to retrieve items such as VHS tapes and Game Boy Colors, which were common back in the early 2000s; they'll also sometimes talk about the Game Boy Advance as if were the hot new thing. Since the game runs in real time, they'll still ask about these items well after they've been rendered obsolete.
The computer item is a '90s-era PC that's hooked up to a CRT monitor, most televisions found in the game are in a 4:3 aspect ratio, and the only widescreen TV is also a CRT, with a VCR hooked up to it, to boot.
Cranky villagers talk about e-mails as if it were an alien concept, invoking Technologically Blind Elders. Nowadays, e-mails have become much more common than the handwritten letters the characters in the game use.
Rover calls Tom Nook with a cell phone straight out of the late '90s / early 2000s.
There was once a "guide" in the early days of the GameCube game about how to turn the game into something resembling Silent Hill.
A common rumor that circulated around forums claimed that a purple bulldog with a black shirt named Brutus, or Burtis, could move to your town and do weird things like talk and send letters in binary, have a house that freezes your GameCube when you enter it, and would move out of town after staying for a day. None of this was true, as was ultimately proven by dataminers, and the only existing image of Brutus was a poorly-edited screenshot of Octavian. This is sort of Ascended Fanon starting in City Folk, where Brutus is Mac's name in French.
There were a few mentions on some sites about a spinoff in the GameCube version called Animal Shootout, a hidden M-rated version of Animal Crossing. In order to access it, you needed to break into Nook's store after closing (how you did this varied from person to person) and suddenly you would be able to steal from and murder villagers.
There are various rumors on how to play "Super Tortimer", a fake NES game Tortimer gives you on April Fool's Day. There is no code for said game as it's a prank and only produces a message saying it's a prank upon examination.
Many fans of the game claim that while the Villagers are very rude in any version that is not the Japanese one, they will eventually warm up to the player. This is not true; the villagers will still be rude to the player and insult them for petty reasons, no matter how much the player helps them.
There were all sorts of rumors about catching a whale in the game. While there is a very rare chance for a giant fish shadow to show up on a boat ride to the island, there's no way to catch it without glitches and cheats. And even if you do manage to catch it, it'll just be an ordinary Arowana with a glitched text box.
At its conception, the game that would eventually become the first Animal Crossing game was vastly different. Originally planned for the 64DD, it was supposed to be a story-driven Role-Playing Game where you could enlist the help of animal characters who could help you in combat, but they had their own set schedule based around the 64DD's internal clock (for example, wolves could only help you at night). After the 64DD was proven to be a flop, this game was heavily retooled. Gone was the combat and the story only got in the way of the enjoyment so that was axed as well. All that remained were the interactive animal characters, item collection and the set schedule. Further ideas were then brought in from another scrapped project, known only by its Working TitleCabbage, to turn the game into what we now know it as, and the real-time clock was built into the game cartridge itself via a battery-operated chip a-la Pokémon Gold and Silver (as the vanilla N64 didn't have an internal clock).
In the international release, the Famicom Disk System version of The Legend of Zelda was replaced with the NES version, indicating that it (and presumably Super Mario Bros.) were meant to be accessible via special e-Reader cards like Ice Climber and Mario Bros.. Internal data in the Japanese version also suggests that The Mysterious Murasame Castle was planned to be included.
Leaked content found from the 2020 Gigaleak indicate that special NPCs were originally intended to be human characters, with complete models for human versions of Joan, Copper, and Booker being found within the leaked files.
The 2020 Gigaleak included early icons for various in-game items, including some that show alternate worldbuilding ideas for the game:
Cherries were originally chestnuts; nuts wouldn't appear as fruit until the introduction of lychees in Animal Crossing: New Leaf.
Medicine was planned to appear in the N64 version, only to be cut for unknown reasons. It would eventually be introduced in e+.
CDs and guitars were planned as items for trading quests; these later became the handkerchief and camera items.
Airchecks were originally going to be MiniDiscs, a real world format of rewritable magneto-optical discs that was popular in Japan as a replacement for cassettes. Presumably, the idea was that K.K. was going to record his songs onto blank MiniDiscs and hand them out to people. Since none of the in-game stereo items are based on MiniDisc players and instead cover shellac records, vinyl records, cassettes, and CDs, the item was changed to a generic music note.
Fish and bugs were going to be represented in the player's inventory by generic icons of a cartoon fish and an insect cage, respectively; the final game has unique inventory sprites for every catchable creature.
Write What You Know: The concept for Animal Crossing was based upon creator Katsuya Eguchi's experience with moving away from his hometown of Chiba to Nintendo's home base in Kyoto. The game's strong emphasis on communal friendship is due to his loneliness at being separated from his family and friends. Since his family enjoyed playing games, but he arrived home from work too late to play with them, he also wanted to create a game where people can play together even when their schedules don't line up.
General trivia
The GameCube ports are fully loaded into RAM during gameplay. Once the town is initialized, the disc can be removed and the game will run with no issues until it needs to save again. This is because they're enhanced ports of a Nintendo 64 game, so their filesize is so small that they can fit into the GameCube's 24 megabytes of RAM in their entirety.
). Ultimately, the three characters and the museum wouldn't debut until Dōbutsu no Mori+/Animal Crossing, implying that technical limitations with the N64 may have kept them out of the series until the GameCube re-releases came to fruition.