Oh Yeah, Luigi Time!
From SmashWiki, the Super Smash Bros. wiki
Oh Yeah, Luigi Time! (known as Luigi's Time to Shine in PAL versions of the game) is a single-player event match in Super Smash Bros. for Wii U. In it, the player controls Luigi, and must defeat a slightly large Wario. After 30 seconds have passed, Giant Mario, who's bigger than Wario, will assist the player.
This event is unlocked by clearing When Lightning Strikes and having Wario unlocked. Completing the event unlocks the right path. Once both the event is completed and Dr. Mario is unlocked, the down path is unlocked.
Completing the event within 30 seconds (before giant Mario appears) awards the Gluey Edge Overalls equipment.