Theory: Picnic Road's Location

Abstract
Picnic Road is located near Pleasant Path/Koopa Village.

Arguments

 * Argument 1: Pleasant Path and Koopa Village are found directly east of Toad Town in Paper Mario, while Picnic Road is found directly northeast of Toad Town in Paper Mario: The Origami King. This would logically place these areas adjacent to each other.


 * Argument 2: Both areas have similar appearances (green grassy areas with white fences) and are noted for having a pleasant atmosphere, having overall similar descriptions in Paper Mario and Paper Mario: The Origami King.


 * Argument 3: Both areas are of importance to Koopa Troopas. With them living in Koopa Village in Paper Mario, and frequenting the Earth Vellumental temple in Paper Mario: The Origami King.