Neighborhorde

The difficult part of this achievement for some will be getting ahold of four controllers. Once you have them, just connect all four and choose PLAY GAME. Press A on each controller until there are four characters sitting on the couch (doesn't matter which ones). Press A a second time on each controller to confirm and then A a final time on your main controller to start the game.

Once the game starts, you should be 50 GS richer. Good luck!