Occasionally, Foxy will replace Diana in Kula's victory animation.
Contributed by DrakeVagabond
Oswald was originally going to be made a playable character in The King of Fighters XII and then was planned to be added to The King of Fighters XIII, teaming up with Iori Yagami and a newcomer who wore a kimono. This idea was scrapped after Mature and Vice were added to the final roster of both games.
Contributed by DrakeVagabond
The game's files contain an animation sequence leftover from its testing phase. It is a short segment from the cutscene that plays before fighting Awakened Saiki, with text that reads:

"And that is the end of this edition. The development team is currently hard at work with the next entry, please look forward to it."
Contributed by DrakeVagabond
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After the second round, there is a chance that Shermie and the original Agents Team will appear in the background of the France stage.
Contributed by DrakeVagabond
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In the China stage, there is a chance that Lin and Fatal Fury characters Tung Fu Rue and Li Xiangfei will appear in the background.
Contributed by DrakeVagabond
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In the Egypt stage, Metal Slug protagonist Marco Rossi, as well as Fiolina Germi and Mars People after the second round, have a chance of appearing in the background.
Contributed by DrakeVagabond
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In the Clock Tower stage, Fatal Fury characters, Wolfgang Krauser, Laurence Blood, Axel Hawk, and Lilly Kane, have a random chance of appearing in the background of the Clock Tower stage. Lilly wears her alternate costume from KOF: Maximum Impact 2.
Contributed by DrakeVagabond
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Hanzo Hattori from Samurai Shodown has a chance of appearing in the background of the Coliseum Rooftop stage.
Contributed by DrakeVagabond
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In the first 2 rounds, Shingo Yabuki and Cosplayer Kyoko will sometimes appear as spectators in the background of the Esaka stage. After the 2rd round, Haohmaru from Samurai Shodown will randomly appear in the background.
Contributed by DrakeVagabond
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The American Sports Team has a random chance of appearing in the background of the Abandoned Factory stage. Also, the damaged bodies of Rocky from Robo Army, and Candy Diamond sometimes appear on the scrap pile.
Contributed by DrakeVagabond
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Moriya Minakata from The Last Blade and Shiki from Samurai Shodown have chances of appearing in the background of the Temple stage.
Contributed by DrakeVagabond
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On the Burnt Remains stage, Charlotte from Samurai Shodown randomly appears in the distant background. The final boss from Garou: Mark of the Wolves, Kain R. Heinlein, and reoccurring antagonist from The Last Blade, Shinnosuke Kagami, also have a chance of appearing in the background, staring each other down.
Contributed by DrakeVagabond
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In the Southtown stage, Art of Fighting characters, Mr. BIG, Karmen Cole, and a poster for Jack Turner's Black Cats, will appear at random between each round.
Contributed by DrakeVagabond
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Richard Meyer from Fatal Fury and Bao from the Psycho Soldier Team randomly appear in the background of the Pao Pao Cafe stage.
Contributed by DrakeVagabond
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Khushnood Butt from Garou: Mark of the Wolves is prominently featured in the background of the Dojo stage. Members of the Anti-Kyokugenryu Team, as well as Sho Hayate from Savage Reign, will randomly appear in the background. All of the featured characters are related to the Kyokugenryu Dojo in their respective series.
Contributed by DrakeVagabond
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After the second round of the Desert stage, when the wind is no longer blowing, Wang Koh-San from Art of Fighting 3 will randomly appear on the left of the stage.
Contributed by DrakeVagabond
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Adelheid Bernstein, Rose Bernstein, and Rodem are prominently featured in the background of the Sky Noah stage, and change their positions on the stage after each round. Rugal Bernstein's image will also periodically appear on the center monitor. And Heidern's image will appear on the monitor Adel sits at.
Contributed by DrakeVagabond
According to background artist, Masatoshi Ohara, the designs for many of the stages were originally early concepts from The King of Fighters XII that did not make it into the final game.
Contributed by DrakeVagabond
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After the first round of the USA stage, Duck King and P-Chan from Fatal Fury, Galford from Samurai Shodown, and a blimp of Mr. Big from Art of Fighting will randomly appear in the background.
Contributed by DrakeVagabond
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Cham Cham from Samurai Shodown, and Tizoc and Khushnood Butt from Garou: Mark of the Wolves will randomly appear in the background of the Brazil stage.
Contributed by DrakeVagabond
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Chris, B. Jenet from Garou: Mark of the Wolves, and a wanted poster for Ryuji Yamazaki from Fatal Fury will randomly appear in the background of the England stage.
Contributed by DrakeVagabond
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Chang Koehan and Cheng Sinzan from Fatal Fury will randomly appear in the crowd of the India stage.
Contributed by DrakeVagabond
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Shingo Yabuki, Hinako Shijou, Ryuhaku Todoh from Art of Fighting, and Nakoruru from Samurai Shodown will randomly appear in the background of the Japan Stage between each round.
Contributed by DrakeVagabond
The initial release of the arcade version suffered from several gameplay affecting bugs. If any of these bugs relating to Hwa Jai, Vice, and Ralf were triggered during a tournament, the player who executed them would either be disqualified or need to reposition themselves on the stage.
Contributed by DrakeVagabond
There are audio files hidden within the game that feature English voices for most of the characters. Many of the voices are reused audio from The King of Fighters XII. However, characters who weren't in the previous game were also going to receive English voice dialogue. The English voices were not a feature in the final game.
Contributed by DrakeVagabond
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Ralf Jones' "Jet Vulcan Punch" move is based on Monkey D. Luffy's 'Gomu Gomu Jet Gatling' move, while using his Gear Second form from Shonen Jump's series One Piece.
Contributed by ProtoSnake