Giga Bowser

Giga Bowser is the final boss of Adventure mode in Super Smash Bros. Melee. He is a gargantuan version of Bowser and could only be fought after completing Adventure mode in normal or higher difficulty within 18 minutes and without using any continues. Additionally, he was a villain in the final Event Match, with Mewtwo and Ganondorf (of the Pokémon and The Legend of Zelda series, respectively) fighting alongside him. Giga Bowser is only playable using an Action Replay.

In addition to being much larger than the original king of the Koopas, Giga Bowser looks far more evil, with a slightly smaller head, spikier, scaled shell, surprisingly more muscular physique, and a new curve to his lengthened horns. Giga Bowser is truly an intimidating sight to behold, and rightfully so; he is far more difficult to battle than his smaller counterpart.

Giga Bowser possessed the same moveset as Bowser, but several moves had an 'elemental' effect; for example, his A+Down move could freeze opponents, and his forward Smash was explosive.

Giga Bowser is officially considered to be a Super Smash Bros. character, not a Mario character. In the game, his icon is not a mushroom (as is the case with Mario characters), but a SSB symbol (as is the case with SSB characters). Therefore, it is unlikely that he will be appearing in any games other than entries in the SSB franchise. However, in Super Smash Bros. Brawl the final smash of Bowser has a mushroom icon, but this is because it is a move of Bowser's.

Giga Bowser returns in Super Smash Bros. Brawl as Bowser's Final Smash. He still takes damage from hits but won't flinch, making him impossible to KO. Because of his large size, he is able to easily attack and KO an opponent. The duration of this move is very short, however there is a glitch that allows the player to remain as Giga Bowser until they self-destruct (cause themself to be KO'd). Oddly enough, while using Giga Bowser, Bowser's icon doesn't change, but that's because it's only a Final Smash move.