After getting caught in the diverse Kanto region, Pikachu was sent over to Professor Oak. However, Team Rocket disrupted the teleportation process, and Pikachu found himself in the middle of Sierra Madre. Pikachu was much larger there, and attempted to disguise himself by using a scarf he found. Due to the fact that Pikachu was in a completely different world, a young trainer was able to catch him before anyone else spotted him.
This scarecrow can be found at 185 Grove Street, Sierra Madre, CA 91024