Sarah caught Poochyena while she was traveling in Hoenn. She was confirmed to be female when Sarah mentioned that she was a girl. Team Rocket attempted to steal Poochyena, Gabe's Pikachu, Pik, and Sarah's other Pokemon. But their evil plan was thwarted by their trainers. Sarah decided to travel with the gang for a while.
Even though she appears mean, Poochyena actually is a very sweet and loving Pokemon.