The cast of characters includes various returning characters from Super Smash Bros. Melee and a variety of newcomers, with a total of 37 playable characters. Some returning characters have been updated or refined since their last appearance, either in terms of appearance, fighting capabilities, or both. For example, Link and Fox have taken on new designs from more recent titles, while Samus has gained the ability to change into a new form, "Zero Suit Samus", by using her Final Smash. Some characters that were present in Melee did not return in Brawl.
Some previously represented series have had more characters added to Brawl. Diddy Kong from the Donkey Kong series and Ike from the Fire Emblem series will make their first appearance in the Smash Bros. series. Other newcomers are the first to represent their series. These include characters such as Pit, representing the Kid Icarus series for the first time since the 1991 Game Boy game Kid Icarus: Of Myths and Monsters, and Wario, from Nintendo's highly successful WarioWare and Wario Land series and an occasional antagonist of Mario's. Solid Snake, the main protagonist of Konami's Metal Gear franchise,[51] and Sonic the Hedgehog[52] from Nintendo's former rival Sega are the first third-party characters to appear in a Super Smash Bros. game.