Darwin, Juarez, Blaster, and Speckles were transported there after escaping from the FBI. They planned to get adopted to escape but only Blaster and Juarez succeeded. Speckles' plan was playing dead but backfires when he was thrown in a garbage truck.
Darwin escaped through a door when Bucky revealed they snuck out every night for nuts while starving himself every morning because he fears Hurley would eat them all. Bucky kicked Hurley out so he can have the cage for himself.