Giga Bowser

Giga Bowser is the final boss of Adventure mode in Super Smash Bros. Melee. As his name suggests, he is a gargantuan version of Bowser and can only be fought after completing Adventure Mode in normal or higher difficulty within 18 minutes without using any continues. In the cutscene that follows when the player accomplishes this, Giga Bowser was created when a Bowser trophy fell onto the Final Destination stage, and then was immediately struck by lightning, right after the player defeats the giant bowser. This revives the trophy, but the energy surge from the lightning causes the strange mutation that turns Bowser into this monster. Defeating Giga Bowser in Adventure Mode awards the player 100,000 points.

Additionally, he is one of the opponents 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.

Giga Bowser returns in Super Smash Bros. Brawl as Bowser's Final Smash. Many of Bowser's moves are hugely powered up in this form, his roar is deeper, and yet some of them are actually weaker than that of the regular Bowser (such as the forward smash). He still takes damage from hits but won't flinch, making him possible to KO only by hitting him when off-screen and at the top border of the screen. Because of his large size, he is able to easily attack and KO an opponent. The duration of this move is very short, though there is a hack that allows players to remain as Giga Bowser until they self-destruct (cause themselves to be KO'd).

In addition to being much larger than the original king of the Koopas, Giga Bowser looks far more ferocious, with a larger body, a spikier scaled shell, surprisingly more muscular physique, and a new curve to his lengthened horns. As well as being an intimidating sight to behold, Giga Bowser is far more difficult to battle than his smaller counterpart.

Giga Bowser possesses the same moveset as Bowser, but several moves have an 'elemental' effect; for example, his down smash can freeze opponents, and his forward smash is 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). 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 and not a separate entity like the Giga Bowser in Super Smash Bros. Melee.

Trivia

 * In Super Smash Bros. Brawl, Giga Bowser's trophy erroneously states that he won't take any damage, which he does (however, he doesn't flinch).
 * Giga Bowser does not have a swim animation; when the player jumps into the water, Giga Bowser will fall right through it and get KO'd.
 * Giga Bowser can't grab items, but he can still have the effects of certain items, such as the Bunny Hood and Superspicy Curry.
 * Giga Bowser's Brawl trophy lacks the game information, "GCN Super Smash Bros. Melee." This is quite odd since his trophy information mentions that game.  A possible reason for this is that Giga Bowser was never playable (except through hacking) until Brawl, or for the fact that it's Bowser's Final Smash trophy.
 * For some odd reason, Giga Bowser is the only transformation Final Smash that has a victory animation. Through hacking it is possible to fight as Giga Bowser through the whole battle and even fight as Wario-Man or other transformation type final smash characters but with everybody except Giga Bowser at the end, on the victory ceremony the game will freeze. Since Giga Bowser is really tall, the player can see his legs and a little bit of his hands clapping together (if the player lost), exactly what Bowser does; Giga Bowser can also do first place animations.
 * Ironically, Giga Bowser's Melee Trophy description ends with the line "Good luck defeating this colossus!" The player needs to have already defeated Giga Bowser in order to obtain the Trophy in the first place.
 * Giga Bowser's trophy pose in Melee is similar to Mario's trophy pose in Brawl.