The toads you see throughout the games (especially the Paper Mario's) are the upper levels of an elaborate trafficking scheme. They sell the heads of the kidnapped for profit
We know that Toad heads can come in multiple colors (we see red and green, among others, quite frequently in the Paper Mario games). It also explains why every single toad is so nice to the brothers all the time; without them, business wouldn't be much, and their fame helps maintain that business.
We're through the looking glass, people.