The Napsack is a special item, that when you hold the 'X' button on your GameCube controller, it makes your pilot lay down and rest. This does not replenish your pilots' health however. It instead allows you to be taken back to the base by your Pikmin. Hwever, one may ask, "Why not walk back there? It's useless!" , well actually, the pilot should be carried back as fast as if all flowered White Pikmin were holding another item, regardless of color; and what it does is let them return to the base, while you make the other pilot do other things, so in the end, you save precious time by having to not bring a pilot back to the base manually, and you also are able to do something else, hopefully useful, in place of that time. Only 4 Pikmin can carry one pilot at a time, but only one is needed to pick him up at all. This ability is similar to that in Pikmin, where you held the D-pad to activate it, 4 to 5 Pikmin could carry Olimar, and also made him impervious, or so said, to attacks.