Memory Card

From SmashWiki, the Super Smash Bros. wiki

A Memory Card is a small device used to save memory/data for games played in the Nintendo GameCube.

One needs a memory card in order to save the things they've accomplished/collected in Super Smash Bros. Melee. In addition, saving data from the game Pikmin on the same card as the player's Super Smash Bros. Melee data will award them Captain Olimar's trophy.