Nintendo does this very well, and the chaos that results from trying to play Mario 3D World with a couch full of friends brings nothing but enjoyment and laughter. What would be simple to do solo becomes nearly impossible with a screen full of characters, and what would be quite difficult to do alone becomes more forgiving with friendly assistance.

In Super Mario 3D World, more accomplices does not mean more accomplishments. Instinctively, every player adopts the personality of the game's iconic Cat Powerup, with every player becoming especially prone to being carried away from the group's shared objectives toward the slightest distraction; I believe Nintendo added the Cat Powerup to the game after initial gameplay testing and noting that the group dynamic matched that of a group of greedy cats rather than a team of playful pups.

Although it's not a priority to me, I would love to add co-op multiplayer to my upcoming game. It would be very difficult to pull off, and I understand that without adding in a "leader" element, it would devolve to cats running about aimlessly. However, as I've said in a previous post, catlike behavior makes for great gameplay.