Lucas

Lucas is the main protagonist of Mother 3, a Japan-only video game. Lucas has debuted in Super Smash Bros. Brawl as a playable character and has appeared in the Smash series since his first appearance in Brawl. He has made a total of 4 appearances in the Smash series.

Super Smash Bros. Melee
When Sakurai updated Ness's profile page on July 17, 2001, he explained that Lucas was supposed to replace Ness as a playable character. However, it was decided that Ness would be retrieved as a veteran fighter due to the cancellation of Mother 3 on the Nintendo 64, the original version that Mother 3 had been worked on.

To quote Sakurai on the matter: Guess what? it was originally intended to replace him [Ness] with the main character of Mother 3 [Lucas], but problems happened during the delay, so we ended up focusing back on the normal idea.

Both Ness and Lucas would later appear in Brawl as playable characters.