Duke's profile information is left blank in the Japanese and Internation releases of the game. The North American version is the only one that features the information.

The European release of the game was the only version to feature an English voice acting.

When creating Hyena's design, Falcoon's main objective was to make a man looks best in a green suit. His wacky gestures and face were based on Boyacky Butsukusa from the Yatterman series.

Duke was originally designed to be a younger man in his twenties with a Japanese sword, similar in appearance to Shinnosuke Kagami from The Last Blade or Kain R. Heinlein from Garou: Mark of the Wolves. He was specifically made to seem as though he's suppressing himself from his true potential. Duke later underwent a number of retakes until the development team requested for a "strong-bodied and serious man in his thirties".

Kim Kaphwan was going to be playable under the pseudonym "Mr. Taekwondo" (similar to Takuma's persona as Mr. Karate in Art of Fighting). However, veteran designers protested the idea, resulting in Kim being replaced with a different fighter. While several SNK's Taekwondo characters were considered (such as Jhun Hoon, May Lee, and Seo Yong Song from Buriki One), a fellow developer suggested creating a female Taekwondo fighter with Kim's "hot-blooded" personality, which eventually formed the basis for Chae Lim. To set her apart, Chae was made to be the struggling student who was not as adept as her peers or mentor but possessed a dominating determination. Ureshino depicts her relation with Kim as a "father-daughter relationship", adding that she is a young woman with Kim's potential.

Mignon Beart was designed to be a contrasting rival to Athena Asamiya. Keywords to creating her persona were "innocent, honest, and a little childish", which Falcoon admits is best seen through her actions rather than her figure. Her design is based on typically "cute idol" traits, particularly her boots, her manner of referring to herself in third-person, and her alternate catgirl costume. Her magical powers were created to counter Athena's Psycho Powers, which is interpreted by Falcoon to be akin to witchcraft.

She was initially not well received by Ureshino and other veteran staff, deeming her to not entirely fit the mood of the King of Fighters universe -though they lightened their impressions after considering the presence of Psycho Soldier members and other "orthodox" characters. As her character further developed, she became the "stupid, but cute" character, Ureshino using the term as a simple means of endearment.

Lien Neville was conceptualized to contrast with Mai Shiranui: Where Mai's character was very cheerful and lighthearted, Lien was made to be more serious and dark. Where Mai represents a "sexy and beautiful [Japanese] kunoichi", Lien represents the "sexy Western femme fatale". Mai wore loose-fitting outfits, while Lien had "tight and constricting" outfits. Mai had is straight and long black hair, and Lein had a short and curly hairstyle. Her curled hair needed several retakes, along with a long trial-and-error process for the game's modelers.

Scenario writer, Akihiko Ureshino, states that the Meira siblings became twin brothers to avoid comparison with other brother characters from other SNK games, such as the Kazama brothers from the Samurai Shodown series and the Jin brothers also from Fatal Fury. He also addresses that the main complaint received from fans was concerns of the brothers "not looking alike"; in response, Ureshino admits that he was also unaware of Alba and Soiree being siblings until much later in production and shares his confusion with fans.

The idea for the "Another" costumes came from the process of designing costumes for the main duo, Alba and Soiree, which led to the idea of the "Another" alternate costumes for every character.

According to the character designer, Tatsuhiko "Falcoon" Kanaoka, both Meira brothers were initially conceptualized to be the KOF counterparts to the Bogard brothers, given the game's setting, Southtown, is the same in Fatal Fury. Several of the brothers' prototype designs were assigned to other characters' alternate outfits; in this case, Alba's prototype design became Rock's alternate outfit, and Soiree's prototype design became Maxima's alternate outfit.