It works by streetpass

streetpass. you get it from walking past people who has a 3ds. you can get travelers and hats or outfits. but theres a lazy way to get streetpass. its netpass. its just like streetpass but online, although you need playcoins.

It works using Streetpass, which runs when your DS is in sleep mode. NetPass and Pretendo's streetpass relay will work as well. I got a couple travellers through NetPass.