In the Japanese version, Dōbutsu no Mori +, two of the NES games that the player could obtain were Gomoku Narabe and Mahjong. The international release respectively replaces these titles with Soccer and Excitebike.

In addition to the multitude of NES games obtainable as furniture items, the player can also acquire a blank NES. On the surface, it appears to be nonfunctional, and interacting with it simply brings up the text "I want to play my NES, but I don't have any software." However, in 2018, dataminers discovered that using the item actually causes the game to scan the GameCube's memory cards for externally installed NES ROM data. By downloading NES ROMs onto the memory card, it's possible to play them in Animal Crossing via the blank NES, including titles not obtainable in the base game. This indicates that at one point in development, Nintendo planned to distribute additional NES games via memory cards.

The ROM loading function additionally enables one to patch NES ROMs after they are loaded, which can be used to install mods for Animal Crossing itself via the memory card.

In the Japanese version of the game, all sixteen player character designs have black eyes, as was the case in Dōbutsu no Mori. In the international release, however, most of them are altered to give them blue, green, or brown eyes; only two variants for each gender remain unaltered.

Four pieces of artwork in the Japanese release of the game were replaced in the international versions:

•The Fine Painting ("Jeanne Hébuterne with Yellow Sweater" by Amedeo Modigliani) is replaced with the Basic Painting ("The Blue Boy" by Thomas Gainsborough).
•The Healing Painting ("Woman with a Parasol - Madame Monet and Her Son" by Claude Monet, a.k.a. "The Stroll") is replaced with the Classic Painting ("Washington Crossing the Delaware" by Emanuel Leutze).
•The Lovely Painting ("Portrait of Irène Cahen d'Anvers" by Pierre-Auguste Renoir) is replaced with the Quaint Painting ("The Milkmaid" by Johannes Vermeer).
•The Pleasant Feeling Painting ("Olympia" by Édouard Manet) is replaced with the Scary Painting ("Ōtani Oniji III in the Role of the Servant Edobei" by Tōshūsai Sharaku).

Of these four, the only painting whose reason for replacement can be concretely inferred is the Pleasant Feeling Painting. Its real-world equivalent depicts a prostitute lying nude in bed, which Nintendo of America likely deemed too mature for a child audience.

The Fine Painting that was replaced in the Japanese release is a different item from the one named the Fine Painting in the English release of Animal Crossing, which is based on Paul Gauguin's "Arearea" and is included in all versions of the game.

With the exception of the Classic Painting, the replacement artwork would become standard for later entries in the series; the only replaced painting to return in a subsequent game is the Lovely Painting, present in all versions of Animal Crossing: Wild World.

Several clothing items were changed between the Japanese and international releases of the game:

•The Three Arc Shirt (a.k.a. the Familiar Shirt) is replaced with the Fortune Shirt, due to the former's resemblance to Charlie Brown's shirt in the American comic strip Peanuts (which had ended its print run in 2000, shortly before the game's release).
•The Tomato Juice Shirt is replaced with the Fishbone Shirt, due to the former's design resembling bloodstains.
•The W Shirt is replaced with the Houndstooth Tee, due to the former's resemblance to the logo of American fast food chain McDonald's.
•The Puzzling Shirt is redesigned to use more pastel colors, also changing the bottom-center square from orange to purple, to reduce the design's similarity to the Rubik's Cube brand of toy puzzles.
•The I Love GC Shirt (itself a redesign of the I Love 64 shirt from Dōbutsu no Mori) is replaced with the Cherry Shirt, due to the former being a parody of the I ❤ NY logo, which is trademarked by the New York Department of Economic Development.

These redesigns are also carried over to Dobutsu no Mori e+.

In the Japanese version, Dōbutsu no Mori +, two paintings that were present in the original Dōbutsu no Mori, the Dreadful Painting and the Novel Painting, are not obtainable in the normal course of play. However, they still exist in the game's code and can be legitimately brought over to a player's save file by importing one from Dōbutsu no Mori (via Nintendo of Japan's now-defunct Data Moving Service), though they can't be donated to the Museum. In the international release of Animal Crossing, however, these paintings are completely removed, and their index numbers instead point to duplicates of the DUMMY furniture item.

It's likely that the decreasing accessibility of these paintings was due to the fact that their real-world equivalents, Edvard Munch's "The Scream" and Piet Mondrian's "Composition with Red, Yellow, and Blue", were still under copyright at the time. The Munch and Mondrian portfolios wouldn't enter the public domain until 2015, well after the Dreadful and Novel paintings were retired from the series.

When waking a villager with the "normal" personality type up from a nap, one of the phrases they can say is "This is not my beautiful house, [catchphrase]! How did I get here?" This is a reference to two different lyrics from the Talking Heads song "Once in a Lifetime" released in 1980.

In an early announcement trailer for the Nintendo Gamecube, Animal Crossing was called (or at least promoted as) "Animal Forest for Nintendo Gamecube", outright referencing the original Japanese title of the game (Dōbutsu no Mori or "Animal Forest" in English). This suggests that either the English localizers were thinking of keeping the game's original title, albeit translated, or the title "Animal Crossing" was not yet finalized.

On August 7, 2002, Nintendo held a contest called the Animal Crossing Official Pioneers Program, where a limited number of participants would be able to receive an early-access copy of Animal Crossing. To apply for selection, one would have to submit a short response of 50 words at most explaining why Nintendo should pick them to be "Animal Crossing Pioneers", with 125 teams of two people (totaling to 250 applicants) ultimately being chosen. Each winner was provided with a specially-marked promotional disc for Animal Crossing, a 59-block memory card, and a calendar spanning September 2002 to December 2003; in addition, winners were given access to an online forum where they could interact with Nintendo of America staff members, completing in-game objectives, providing feedback, and participating in online chats.

When the player meets Mr. Resetti for the sixth time, one of his lines reads "You got another think comin'!!!" This line contains a typo by mistakenly saying "think" rather than "thing."

Animal Crossing for the GameCube is a direct port of the Japanese-only Nintendo 64 Dōbutsu no Mori (Animal Forest) so it takes up very little space on the GameCube disc. The entire game is loaded into the GameCube's RAM, and as a result, after the player enters their town they can remove the game disc from the GameCube and continue to play the game normally.

Sometimes villagers will request the player to track down their "Pokémon Pikachu". This refers to the virtual pet toy of the same name, rather than the creature itself.

A mole named Mr. Resetti will pop up to scold the player if they reset the game without saving. On the sixth and random subsequent times, he will force the player to copy what he says by typing it in, and will not leave until they do so correctly. However, typing in the following phrases will trigger special dialogue where Mr. Resetti scolds the player even more:

"no", "NO!", "jerk", "Die!", "Loser", "RESET", "freak", "Creep", "no way", "Leave!" "No Way!", "shut up", "go away", "Pinhead", "Dirtbag", "Scumbag", "Shut Up!", Go Away!", "Butthead", "Bite me!", "U R UGLY", "groundhog", "You stink", "I + Reset", "You suck!", "I hate you", "Moles suck", "Who Cares?".

Mr. Resetti was added into the game when developers noticed that, during play testing of Animal Crossing, many players were resetting their consoles to let the stock in Tom Nook's store change. They felt that this was toying too much with the game's mechanics and added Mr. Resetti in to discourage this behavior.

In the Japanese versions, Jane has brown skin, white fur, tired eyes, and large, pink lips. This design was heavily altered during localization to avoid any possible racial tension.

If the player goes to another town and resets the game before going back to their town, the next time they load up their profile they will start with a Gyroid face.

There are numerous unused items in the game's code, all of which can be accessed with cheats. These include:
• A blue fish, possibly used to test the fishing function.
• DUMMY, a glitch item appearing as a white triangle with Japanese text on it reading "ダミー", which translates to "DUMMY", hence the name. Once in an Igloo, you obtain the item in a similar way to other furniture. The animal might want to play a game where he or she will ask you to pick two cards. One card you have to buy something and one card you will get a free prize. The prize card may sometimes be a DUMMY card.
• A glowing yellow box that moves back and forth, can push the player around (sometimes making them float), and can modify the spread of Paper Airplanes.
• A tool labeled "Sickle", which makes the player function as if they had nothing in their hands. Strangely, it appears as a toolbox when dropped, a feature that only appeared in Wild World and New Leaf.
• An "Unknown Item" that appears in the player's inventory as a box with a question mark, and appears in homes as a clone of the DUMMY item.
• Paper Airplanes, which, if you place on the ground, walk off screen, and come back, will duplicate itself. Pressing the A button while on top of the paper airplane will make it disappear visibly, but will still exist in the system's memory. Letting the airplane multiply too much can crash the game.

The game has an entire debug mode which can be activated by setting the disc ID version field to 0x99 through using a hex editor and change byte #7 (0x00000007) of the ISO/GCM file. It works on all versions of the game.

The "forest map select" from Doubutsu no Mori still exists in the game's code, but there's no easy way to access it.

The train conductor 'Porter' is based off of the Japanese song 'The Monkey Palanquin Carrier'. This is the reason he's a monkey.