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.

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.

According to series creator Masahiro Sakurai in a 2024 video, ideas for the series' name were first brainstormed by team members at HAL Laboratory, while the "Bros." part of the name was picked out by its president Satoru Iwata during a meeting with him, Sakurai, and Ape Inc. founder Shigesato Itoi. Iwata's reasoning for adding Bros. to the title was that despite the game's roster not all being "brothers", he believed the word added the nuance that they were "friends who were settling a little disagreement" instead of just simply fighting.