He first appears in Episode 6, leading the group to the hot spring resort. Although he tricks the group into entering the Beastmen's trap, he helps Kamina onto the Beastmen's Gunmen after it is revealed. When the Gunman is defeated, he quietly tags along with Kamina's group.
He remains in the background for most of the series, but when Simon finds Nia and brings her back to the Dai-Gurren, he unofficially becomes her caretaker. He saves her several times on the way to Teppelin, including distracting Guame when he held Nia at gunpoint and catching Nia when Yoko forced Adiane's personal Gunman to release her. When Nia prepares to board Gurren Lagann to confront her father, Old Coco encourages her on with a nod.
After the timeskip, it is revealed that Old Coco is, in fact, a Beastman who cared for Nia when she was raised in Beauty Village, and continued to do so even after she was no longer the princess of Teppelin. When Nia is taken into Anti-Spiral space, he presents Simon with the flag used during the fall of Teppelin, which Simon uses to officially christen the Super Galaxy Dai-Gurren before embarking on his quest.
As expected, Old Coco greets Nia after she returns home in the last episode, giving her the wedding dress he made. This is the only time he is heard speaking in the entire series.