World 1-2: Unlimited Lives:
When you enter the pipe at the start of the level you will come to a wall you can climb. At the top of the wall you will find a turtle and a power-up block. If you smash through the two purple blocks on the ground using a butt stomp you will find another turtle there. Stomp on that turtle without hitting it's shell and walk off from the left onto the shell. If you manage to do this correctly it will break the blocks then bounce back and forth giving you unlimited lives.
Unlock Luigi Bros. Mini-Game (Alternate Way):
An alternate way of unlocking this mini-game that is based off the original Mario Bros arcade game is to have a saved game file from Super Luigi U. On your Wii you, play as Rosalina and complete Star World 2.
Unlock Luigi Bros. Mini-Game:
Complete Worlds 1 through 8 and then tap the Luigi icon in the bottom left corner on the GamePad to unlock this mini-game that is based off the original Mario Bros arcade game.