In the Super Smash Bros. series, which character was the first one to return to the series after being absent from a previous game?

Dr. Mario was the first character to return to the Super Smash Bros. series after being absent from a previous game because he made his debut in Super Smash Bros. Melee as a separate character from Mario, but did not appear in Super Smash Bros. Brawl. However, he made his comeback in Super Smash Bros. for Nintendo 3DS and Wii U, thus becoming the first character to make a return after missing a game in the series.