Play Classic / Adventure / All-Star / Stadium Modes: Each character has specific unlock criteria (e.g., "Clear Classic on Hard with Mario" → unlock Luigi).
VS Matches: Play X matches → challenger appears → defeat to unlock.
Secret Characters (Examples):Goku (Classic Hard no continue), Ichigo (All-Star clear), Lloyd (VS matches), Sora (Adventure), Black Mage (Stadium). Exact criteria change per version.