Casey was just a Cub Student at Pai Zhuq, and had only been there a week, when his life changed. After he stood up to Jarrod, and took up for the little guy, Master Mao saw greatness in him. Mao chose Casey to take Jarrod's place, in guarding the spirit of Dai Shi, along with Theo & Lily.
After Dai Shi escaped, and Master Mao was destroyed, Casey, Theo & Lily went to Ocean Bluff to find their new master, RJ. Now with the powers of the Red Ranger at his command, Casey has to learn how to be a leader. He all ready has the power & ability to fight for good and stand up for those in trouble. But he still has doubts about himself.
Once Casey mastered the Shark Technique from Master Finn, and the others had Mastered their new techniques, the Rangers all thought they were unbeatable. However, Dai Shi had been training with masters as well. When they battled against the new more powerful Dai Shi, the Rangers lost, and would have been destroyed had RJ not intervened and gave himself.
The Rangers realized that their over confidence had been their downfall, but they didn't let that get them down. The team journeyed to the Spirit World, with the help of Master Mao. Once there, they met their new Masters. Master Rilla sent Casey on his journey to conquer his fears of the unknown. Upon completing his journey, Casey not only gained the power to summon the Gorilla Zord, but he also gained the power to morph into his Jungle Master Mode.
Casey's Tiger Spirit was stolen from him by the Phantom Beast General Whiger. But the Red Ranger learned, thanks to RJ, that the spirit does not make the person stronger, but the person is what makes the spirit stronger. While Casey was still able to morph and summon his Zords, it took a heavier toll on him.
Because Whiger was unable to destroy Casey, his Rinzin powers were taken away & he was banished by Dai Shi. In hopes of regaining his honor, Whiger tried to battle Casey, but lost. During the fight, Whiger was about to fall over the side of a cliff, but Casey saved him. This kindness shown by Casey helped Whiger realize that the Rangers were not his enemy, but Dai Shi was. In order to repay the kindness shown to him, Whiger gave Casey his Tiger Spirit back, just before he faded away.
After much of the year had passed, the time finally came to Casey, Theo & Lily to go through their Pai Zhuq Masters Test. For his test, Casey had to battle and defeat Master Finn. However, Casey was not confident in himself, or his skills. So in his battle, while he did manage to beat Master Finn, he did so by watching what Theo & Lily did. It is for this reason that Casey failed the test. A Pai Zhuq Master knows his or her way & path, and cannot rely on others to show him how.
Casey took his failure hard, but when running to try and blow off some steam, he discovered something very important. He saw Camille being attacked by the last three Phantom Beast Warriors. Just as she was about to be destroyed, Jarrod, the real true Jarrod, jumped in, saved her & destroyed two of the three warriors. Casey witnessed that Jarrod was still there, but wasn't about fully help himself, due to the overwhelming power of Dai Shi.
When Casey returned to JKP and tried to explain what he saw to Theo & Lily, they refused to believe that Jarrod was good, or could even be saved. Thus leaving Casey as the only one wanting to save Jarrod.
After talking with Dominic and learning that Jarrod's childhood was the reason behind him originally turning into a bully, Casey went to Dai Shi's temple, to get Jarrod back. On his way, Master Mao confronted Casey and tried to tell him that there was no hope left for Jarrod. But Casey refused to believe that. Deep down, Casey felt guilty for not only Jarrod's fall into Darkness, but for Dai Shi escaping in the first place. Had Casey not gone to Pai Zhuq, then Jarrod would not have gotten kicked out & Dai Shi would not have been released. The Tiger warrior continued on his own path, defying his original Master.
When Casey finally arrived, the battle between the Red Ranger & Dai Shi began. Both fought hard, but the Red Ranger refused to give up on himself & Jarrod. Finally, the Red Ranger was able to beat Dai Shi, but instead of destroying him, he tested Jarrod. He told him if Jarrod was really gone, then Dai Shi could destroy him. When Casey turned his back to wait, Dai Shi started to attack, but Jarrod stopped him. Through his kindness & friendship, Casey was successful. Jarrod was able to free himself from the spirit of Dai Shi.
But Dai Shi wasn't finished yet. The evil spirit attacked Jarrod, and Camille for defending the human. Casey came to their rescue and used his Tiger Spirit to attack and weaken Dai Shi, allowing them to escape the temple.
Casey & Jarrod then fought alongside one another; Casey as the Red Ranger & Jarrod as the Lion Warrior. Together they were able to beat Scorch.
After Scorch was beaten, Casey's Master Stripes appeared on his arm. RJ explained that when Casey chose to defy Master Mao & believe in his own convictions, path to Master Hood became his destiny.
In the final battle against Dai Shi, it took help from Camille & Jarrod to help weaken Dai Shi. But only the chosen three could destroy Dai Shi. Together Casey, Theo & Lily reached a level of power no one had ever achieved before. This powerful attack was able to destroy Dai Shi for good.
After the battle was over and won, Casey became the new Master Teacher at the Pai Zhuq school.