Unused Characters

An Intended Character is a character that was planned to be in a game, but taken out due to certain reasons. Usually, the intended characters get put in later installments of the game, but some characters are not.

Super Smash Bros 64
It can be assumed that these characters were cut due to system limitations or time restraints. Pit was removed because of clipping issues with his wings. Meowth was never considered to be a playable character after this, but he did appear as a Poke Ball Pokemon in every installment.
 * Bowser
 * Mewtwo
 * King Dedede
 * Princess Peach
 * Meowth
 * Pit

Super Smash Bros. Melee

 * King Dedede
 * Meta Knight
 * Lucas
 * Wario:'
 * Wolf

King Dedede and Meta Knight were planned to be in SSBM, but Sakurai didn't want to over-represent his own characters, so they were cut. Lucas was originally planned to replace Ness. But problems with the release date caused to Ness' return. Wolf was intended to be in the game along with Falco. Falco was added, but Wolf only made a cameo in the intro. Not much is known about Wario's appearance, but he was considered.

Super Smash Bros. Brawl

 * Dr. Mario
 * Mewtwo
 * Roy
 * Toon Zelda/Toon Sheik (Tetra)
 * Plusie and Minun (most likely)
 * Dixie Kong

The characters cut from Brawl are known as the "Forbidden 7". Dr. Mario was close to getting in, but was cut due to time restraints. Mewtwo was the farthest character in development, with many files existing to prove his appearance. However, time restraints forced him to be cut. Roy also fell to the same fate as the other Melee fighters. Toon Zelda was also supposed to be in the game, but was cut. The reason why is unknown. Files were discovered that were titled "pra&mai", which led people to believe Plusle & Minun were planned in the game, due to the fact "pra" was the first syllable of Plusle's Japanese name, and "mai" was the first syllable of Minun's Japanese name. It is unknown if these truly are the characters found in the file. Dixie Kong was planned to make her debut alongside Diddy Kong, but was most likely cut due to time restraints.

Super Smash Bros. for Nintendo 3DS and Wii U

 * Ice Climbers

Sakurai stated that he and the development team had trouble adding the Ice Climbers into the game due to the 3DS' hardware limitations. Files proving their existence were found, though, in a glitch in the game. When playing as Villager against three Dr. Marios, the crowd will cheer "Nana! Popo!" instead of the Villager's usual cheer. The Ice Climbers are the only known cut characters.

Trivia

 * Meowth is the only character in the original Super Smash Bros. (series) to not get in any of the games later on.
 * Roy is the only character from Melee in the "Forbidden 7" to not come in later installments of the game.