After the fight with Centipede, before Alice eats the toadstool to return to her normal size, she will say "I wish I were hallucinating. What a horrible choice. Eat a toadstool or remain food for insects."

There is an unused take in the game's files that features a slightly different ending. "I wish I were hallucinating. What a horrible choice. Eat a toadstool or become a meal for insects."

This unused take, while it is in English, does not appear in the English dub's files, only being present in the files for the Spanish and German dubs.
Contributed by Takahashi2212
When the game's soundtrack was released, composer Chris Vrenna added lines from the game to every song. This was done as a method of retelling the game's story through audio alone.

Notably, some lines used on the soundtrack (such as the line used in the song "A Happy Ending") actually went unused in the final game.
Contributed by Takahashi2212
The game's official soundtrack contains songs not found in the game. According to the game's composer, Chris Vrenna, he actually composed many more songs had been required for the game, and he decided to release all the unused songs alongside the used songs on the game's official soundtrack.
Contributed by Takahashi2212
When the game was released in Japan, the game's name was changed to "American McGee's Alice in Nightmare" as a play on Alice in Wonderland.
Contributed by Takahashi2212
The Save/Load screen features the brand "Bandersnatch Opticals" on it. This brand is named after the Bandersnatch, a creature featured in Lewis Carroll's "Through the Looking-Glass, and What Alice Found There", specifically the piece "Jabberwocky".
Contributed by Takahashi2212
In order to accurately capture the Victorian era, composer Chris Vrenna disallowed himself from using modern instruments.

The soundtrack was largely composed using instruments of the time, such as zithers and autoharps, toy instruments, and various children's toys, such as jack-in-the-boxes. Ambient noise and strings were then added to the songs to give the songs a more creepy feeling.

In order to make the music more organic sounding, Vrenna built the rhythms of the songs based on various environmental samples such as clock ticking, ratchet noises, and door slams.
Contributed by Takahashi2212
There is a different version of part of the Red Queen's speech to Alice in the game's files. This version uses the Red Queen's normal voice, as opposed to the distorted, deeper voice featured in the final game.
Contributed by Takahashi2212
According to concept art, Alice's dress was to feature the symbol of Ceres as opposed to the symbol of Venus as seen in the final game.
Contributed by Takahashi2212
A console port of the game was planned but never came out. This is most likely due to the closure of Rogue Entertainment in 2001.

The game wouldn't see a console release until 11 years after it's release, when it was released for Playstation 3 and Xbox 360 as a extra included in the sequel, Alice: Madness Returns.
Contributed by Takahashi2212
When talking to Turtle at the beginning of the level "Dry Landing", Alice will say "I'm not on holiday."

This line was originally meant to be "I'm no bloody tourist!". This unused line was recorded, and can be found in the game's files.
Contributed by Takahashi2212
There are eight takes of the Red Queen saying "Off with her head" in the game's files. Only one take is ever used in the final game, meaning that the other seven takes go unused.
Contributed by Takahashi2212
There's an unused alternate version of the game's ending theme called "finale_bad.wav" in the game's files. This implies that at one point, the game was to feature multiple endings.
Contributed by Takahashi2212
This game was the first M rated game published by EA. According to American McGee, he fought for the rating because he didn't want parents to buy the game thinking it was for children.

In retrospect, McGee stated he regretted fighting for such a high rating, believing the game wasn't violent enough to warrant it.
Contributed by Takahashi2212
In the console versions of the 2011 rerelease, the main menu and loading screens are rendered in 4:3, as opposed to 16:9 like the rest of the game. As such, they feature a border. This border is not featured in the PC version of the rerelease, since the main menu and loading screens are rendered in 16:9 like the rest of the game. However, the border is still in the PC version's files as "border1_left.tga".

Similarly, the console versions also feature a title screen, which goes unused in the PC version since neither the 2000 original or the 2011 version have a title screen. This is also in the PC versions files, as "title_bg.tga".
Contributed by Takahashi2212
In one of the cutscenes in the game, Alice will say the line "I shouldn't think so. I'm a person, and just now I wish to become very small. About this big." However, there is a different take of the line in the game's files that goes "I shouldn't think so. I'm a girl, and just now I wish to become very small. About this big.", replacing the word 'person' with 'girl.'

Both the original release and the 2011 rerelease use the version with "person" in it, so this different take goes unused.
Contributed by Takahashi2212
The symbols on Alice's dress have changed throughout promotional artwork and the several releases of the game.

In original promotional artwork, the symbols are the symbol of Neptune and the symbol of Jupiter. In game, the symbols are the symbol of Venus rotated 45 degrees to the left, and a sextile.

In the 2011 rerelease of the game, the symbols are the symbol of Eris, and the symbol of Jupiter. This makes the design fall in line with its appearance in the sequel, Alice: Madness Returns.

When American McGee was asked about the symbols he said "the difference in symbols might have to do with poor communication/planning and/or might have to do with the marketing department being overly sensitive about the symbols and their meanings. Too much time has passed for me to remember exactly what caused the differences."
Contributed by Takahashi2212
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In the White Castle located in the Pale Realm, there is a portrait of Lewis Carroll, the author of the original Alice in Wonderland novels.
Contributed by Boyobmas
In a prerelease trailer for the game, the background music is a reprise of several songs spliced together from Sleepy Hollow and Edward Scissorhands, both composed by Danny Elfman.
Contributed by Electra
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The cover of the game, showing Alice holding the Vorpal Blade with blood splattered on her dress, was deemed too violent for store shelves in some regions. Alternate versions of the cover include her holding the Playing Cards or Ice Wand instead, with the blood removed.
Contributed by Electra
During development, Marylin Manson was involved in producing music for the soundtrack. He left the production team early on, but his contributions still made it into the final game, mostly in the influence of alchemy and The Mad Hatter.
Contributed by Outofmind23
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In early screenshots and beta art work, Alice had two different necklaces. The first was an A pendant and the other was an upside-down cross. Neither made it to the final version, in which Alice wears her omega necklace.
Contributed by gamemaster1991