Katrese's Mightyena is her third Pokemon that she obtained. She first appeared as a young Poochyena in The Poochyena Forest.
Mightyena as an Poochyena lived with her parents and her siblings before joining Katrese, but she and her siblings were captured by Team Rocket. Her parents tried to save her, but they were captured as well. James said they would get a huge payment for capturing the Poochyena and the Mightyena. Poochyena managed to escape and she went to get help. She ran into Katrese and told Pik what happened. Katrese and her friends decided to help Poochyena rescue her family. Team Rocket noticed that they were missing one Poochyena and Jessie was enraged and sent Pumpkaboo to find Poochyena and capture her. Poochyena was almost captured by Pumpkaboo, but Katrese had her Braixen and Mudkip fight Pumpkaboo off to protect Poochyena. The kids and Cilan and Poochyena managed to reach Team Rocket and Jessie used a metal grabber to grab Poochyena, Braixen, and Mudkip saying that these rare Pokemon would get them lots of money. James used a metal grabber to grab Gabe's Charizard, Char, Pik, and Crystal's Vaporeon and placed the Pokemon in the net and tried to escape with the captured Pokemon. But Gabe sent out her Espeon, Eve, and Crystal sent out her Bulbasaur, James tried to grab both Pokemon with the metal grabber, but they were blocked by the Mightyena who had managed to escape and distracted Team Rocket while the kids freed the Pokemon. The Pokemon were reunited with their trainers and the Mightyena helped blast off Team Rocket. Poochyena decided to travel with Katrese and her parents, the Mightyena accepted her decision. Poochyena has participated in many Pokemon contests with her trainer. During a battle with Gabe, Poochyena evolved into a Mightyena. In one episode, Jessie from Team Rocket attempted to steal Mightyena for her own purposes, but Katrese rescued her and sent Team Rocket blasting off.
Mightyena as an Poochyena is a friendly and loving Pokemon living with her parents before joining Katrese. She loved her mother. But when they were captured by Team Rocket, she being loyal and loving to her family went to get help. She decides to join Katrese after Katrese shows how much she cares for her and her parents see that Katrese would take good care of her. She is used in many of Katrese's Pokemon battles and showcases. She is friends with Erika's Dedenne as the two often play together.