From Bulbapedia, the community-driven Pokémon encyclopedia.
Inside of Truck (Japanese: トラックのなか Inside of Truck) is the location header used by Pokémon Ruby, Sapphire, and Emerald when the player is in the truck that appears right at the beginning of their journey.
Normally when the player exits the truck, no location header is displayed. However, in Ruby and Sapphire, if the player saves the game while Inside of Truck, reboots it, then exits the truck, the location header pop-up of Littleroot Town is displayed; this does not occur in Emerald.
In Pokémon Omega Ruby and Alpha Sapphire, it is instead labeled as ??? (Japanese: ？？？ ???), index number 114h.
In the manga
In the Pokémon Adventures manga
At the start of the Ruby & Sapphire chapter, in Creeping Past Cacnea, Ruby was seen inside the truck with his Pokémon, while his mother was driving to their new home in Hoenn. Ruby was sewing pieces of clothing for his Pokémon, and taking care of them. The Truck got stuck in the mud, but Rara (currently a Ralts) used Confusion from the inside to telekinetically lift the truck.
In other languages