For some reason, the announcer says Fox differently in the Japanese version than in the International version, even though Fox is a character with no name differences in any region.

The Fighting Polygon Team is called Dummy Corps in the Japanese version.

According to a page on the Japanese Super Smash Bros. site, Mewtwo was planned to be playable, but was cut; Bowser and King Dedede are also mentioned as having been cut, though no other information is available.

Charles Martinet is misspelled as Charles Martinee in the game's credits.

It is impossible (at least without the use of a cheat device) to clear all eight digits in the points counter in 1P mode.

Captain Falcon has the most usable costumes in the game, with six. Most characters have four or five. Yoshi also has six, but only four are usable outside of hacking, as two only appear in the single player mode.

When the Announcer introduces Metal Mario, his voice becomes slightly metallic. Although it may just be to place emphasis on Metal Mario's metal composition, the Announcer's voice sounds noticeably deeper and it does not change like that for any other character in Classic Mode.

Luigi takes his appearance from Super Mario World, having purple overalls rather than dark blue. However, this is not true of his artwork.

Captain Falcon's "Congratulations!" screen is the only one to use a pre-existing image from an original game, in this case, the first unlockable title screen from F-Zero X.

Captain Falcon is the only playable character that doesn't use his own head for his stock life icon. Instead, he uses a Falcon.

While all other characters show their skeletons upon being hit with an electric attack, Samus's suitless outline becomes visible instead.

In the character select screen, the characters (excluding unlockable characters) are placed in the order of when they first appeared in their respective titles, starting with the oldest, Mario and Donkey Kong, and leading to the most recent, Pikachu.

Luigi's voice is just a pitch-altered version of Mario's.

According to an interview with Satoru Iwata, Masahiro Sakurai intended for the characters to use Final Smashes in this game. It was taken out due to hardware limitations. This concept was held off until Super Smash Bros. Brawl. Going in the debug menu you can find 3 sound files. 2 of them of Ness saying "PK" and "Starstorm!". The third is Captain Falcon saying "Come On!".

The original prototype for Super Smash Bros. was a four-player fighting game designed by Masahiro Sakurai and programmed by Satoru Iwata tentatively called "Dragon King: The Fighting Game". The game was designed specifically for the Nintendo 64's joystick to see how it could be used in a multiplayer environment. The signature concept of Nintendo characters fighting each other was not initially present, but would soon be implemented as the first idea Sakurai thought of to make his game stand out, as fighting games did not sell well and most of his original concepts felt better suited for arcade fighting games rather than home-console fighting games. A subsequent prototype featuring Mario, Donkey Kong, Samus, and Fox as playable characters was then made without sanction from Nintendo's higher-ups and they were not informed of its existence until Sakurai was sure the game was well-balanced. When Iwata initially presented the idea of the game to Shigeru Miyamoto to gain approval for the use of Nintendo characters, he turned it down. However, Iwata did not tell Sakurai this and convinced him to pitch the prototype to Miyamoto anyway, which later got his approval.

Little is known about Dragon King's gameplay or design, and all information known about the game comes from interviews and a handful of images shown when the game was in an alpha stage. No gameplay footage has been demonstrated, and a working prototype has not been made publicly available. Images of the game, however, show that much of the core gameplay was similar to Super Smash Bros., featuring damage percents, arenas with platforms, and combatants that do not strictly have to face one another. The tall, thin build of the unnamed fighters and their kicking and punching techniques also appear to be relatively similar to that of Captain Falcon. The most widely-known stage background featured in the screenshots is a photo taken by Sakurai of a Ryūō-chō neighborhood in Yamanashi, Japan, which is where HAL Laboratory's headquarters are based, where the game was being developed, and what the prototype was named after. The "Ryūō" in Ryūō-chō means "Dragon King".

Falco Lombardi, Slippy Toad and Peppy Hare were at one point considered for Fox's alternate costumes, before being scrapped in favor of generic recolours. Falco would eventually appear as a unique character in Super Smash Bros. Melee, and while Slippy and Peppy to date still have not appeared, alternate costumes that change a character outright would become a Smash feature starting in the 3DS and Wii U games, with Alph for Olimar, the Koopalings for Bowser Jr, and Alex, Zombie and Enderman for Steve.

When looking for additional characters based on pre-existing fighters to include in the tail-end of Super Smash Bros.' development, Masahiro Sakurai had considered including Clefairy from the Pokémon series as a derivative of Kirby's skeleton. Ultimately, he chose Jigglypuff, as he felt its personality stood out more as a weaker character likely to be defeated.

Despite being boss characters in the game's 1P Mode, Giant Donkey Kong and Metal Mario are competitively considered some of the worst characters in the game and a clear downgrade from their root characters when modded into Vs. Mode.

Mario and his Special Moves in this game are based off of the "Shoto" style of Fighting Game characters, most specifically the character Ryu from Street Fighter. For example, like Ryu, Mario has a Hadoken-like "fireball" attack with his Neutral Special (Fireball), A punching uppercut similar to the Shoryuken via his Up Special (Super Jump Punch), and a spinning tackle akin to Ryu's Tatsumaki Senpukyaku in the form of his Down Special (Mario Tornado). However, while Mario's moveset would change in later games to be less Shoto-esque, Ryu himself would be added into the Smash series and make his debut as a fighter in Super Smash Bros. for Nintendo 3DS and Wii U.

The 3D portraits on the character select screen are based on character artwork from some of their home games. Mario's render is from Super Mario 64; Link's is from his artwork for The Legend of Zelda: Ocarina of Time; Donkey Kong's Donkey Kong Country artwork is the basis for his Smash portrait; Yoshi's comes from Japanese artwork for Yoshi's Island; Kirby's is from Kirby's Adventure artwork; Fox's is taken from Star Fox 64; Captain Falcon has a 3D realization of artwork from F-Zero X; Pikachu and Jigglypuff are 3D versions of Pokemon Red & Blue concept art; Samus Aran's comes from Super Metroid; Ness's is a redone done version of his EarthBound art; And Luigi's appears to be taken from Mario Kart 64.