In Street Fighter III: 2nd Impact there is an unused female voice that doesn't match either Elena or Ibuki. It's possible these voice lines belonged to an earlier version of Makoto, as she was originally meant to debut in this game but was moved to 3rd Strike due to time constrains.

In a 2003 interview with the game's producer Noritaka Funamizu published in the 15th Anniversary Street Fighter limited edition DVD set, Funamizu stated that at the time he had been pushing Yoshiki Okamoto to include Chun-Li in the game, and Okamoto agreed to it, if 3rd Strike were to be developed. At the time, the team thought of making a big roster for 3rd Strike, and Okamoto was more insistent. He also stated that if Chun-Li wasn't included in the game, she wouldn't have gained the same impact as before. Okamoto thought of Chun-Li as the mascot of Capcom.

Funamizu also stated that Chun-Li's absence was the team's number one complaint they received from players for not including her in the previous Street Fighter III games. However, he stated that the team did wanted to include her in the games.

In a 1999 developer interview published in Gamest magazine, the concept art for Ibuki's "Yami Shigure" move was originally going to be a normal special attack, but was changed to Super Art after many people complained.

Originally, Ken was going to have more moves, but that idea was scrapped, due to his "Shoryuken" move being too strong.

Makoto was originally planned to be introduced in "Street Fighter III 2nd Impact: Giant Attack", but time restrictions led to her not being included.

The hand sings used by Oro during his animations for blocking/parrying an attack, using his normal fireball, or using his Yagyou Dama super art, are know as mudra, which are symbolic or ritual gestures from the Hindu and Buddhist faiths; later on incorporated into various eastern styles of martial arts. Additionally, Oro draws Ki energy from a specific part of his body depending on where his hand is placed, for example, if Oro placed his hand on his head he's drawing energy from the brow chakra, and when placed on the chest he's drawing energy from the heart chakra.

According to the "ALL ABOUT Capcom Fighting Games 1987-2000" book, Alex was originally supposed to be the main character of SF3, but this was changed because he wasn't recognized as a hero character compared to Ryu.

Chun-Li makes a cameo in Ryu's background during the New Generation and 2nd Impact games; she can be seen bathing on the top left of the stage.

Screens from early versions of the game show that Ryu originally had different art at the select screen. This early version also has different colors on the HUD, and the "PLAYER SELECT" text was blue instead of yellow.

In the game's data there is a remix of the "Jingle Bells" Christmas song that goes unused in normal gameplay. This music was most likely used in a location test build of the game, which had Christmas and New Years messages for the player. As these messages were removed from the final version, the Jingle Bells theme also goes unused, although you can still play it in the sound test.

A prototype version of Hugo can be found in the game data for Street Fighter III: New Generation, with only his basic moves finished and placeholder graphics. Performing certain attacks on him may cause him to become invisible or freeze the game.

In Street Fighter III: New Generation, when loading the main menu the game also loads in an unused image for a ghost that looks very similar to the Ghosts from Pac-Man.

In the English release of Street Fighter II, one of Ryu's quotes to defeated opponents is "You must defeat Sheng Long to stand a chance." "Sheng Long" is a mistranslation of Ryu's flying uppercut move Shōryūken (昇龍拳) stemming from the first two Japanese characters meaning "shēng lóng" in Chinese pinyin. As a result, players mistakenly thought that Ryu was referring to a person named Sheng Long instead of his Shōryūken, and that he was a secret playable character.

Amidst a swarm of fan mail to gaming publications asking how to unlock Sheng Long, the American magazine Electronic Gaming Monthly published a guide to fight him as a secret boss for their annual April Fools' prank in 1992. Photoshopped screenshots of Sheng Long fighting Ryu were created by editor Ken Williams, who also wrote "ridiculous requirements" to find him that were meant to imply he was not real, but were actually attempted by players. In response to complaints, they revealed at the end of the year that Sheng Long was a hoax, and expressed surprise over it gaining worldwide coverage as other publications in Eurasian countries reprinted the guide without their permission.

Sheng Long was brought back for a second April Fools' prank in 1997 in response to rumors that he could be in Street Fighter III, creating hand-drawn art of him and claiming he was the localized version of the real non-playable character Gouken. Despite adding more obvious clues to it being a prank, according to the magazine's June 1997 issue, this second prank was so convincing that Capcom of America allegedly fell for it and called their Japanese headquarters to ask why they were not told he was in the game.

Sheng Long left a continuing influence on video game hoaxes and the Street Fighter series, leading to a scrapped official appearance in the game adaptation of Street Fighter: The Movie, and Capcom pulling their own Sheng Long pranks in 2008 and 2017. In 2023, Sheng Long made his first canonical appearance in the series in Street Fighter 6 as a non-playable opponent using Ryu's fighting style, and can be fought in the World Tour mode after completing the game.