Transitional episodes have an odd effect on me. Most shows don’t have the courtesy to provide them, as it’s necessary to keep the story and character development moving forward, but I think Gainax was able to pull it off with the introduction of a new character, a dramatic (if temporary) shift in presentation style, and a little reshuffling of the deck.
After the events of Episode 8, Tengen Toppa Gurren Lagann finds itself in the midst of a serious shift in character dynamics. When Yoko arrived in Simon’s village, her experience and competence acted as a serious foil to Kamina and Simon’s naïveté and bumbling ways. Kamina was already a foil for Simon’s lack of ambition and self-confidence. Kamina and Yoko provided contrasts for Simon’s defining characteristics. Each shared characteristics with him as well. Kamina was just as ignorant as Simon, and Yoko is every bit as practical as Simon. This provided a great deal of balance in their interactions.
Alas, change is an inevitable component of any good story, and Gainax provided plenty last week. Episode 9 is a transitional point in the story, with Simon stricken by grief and consumed by anger, without anybody to put a check on his behavior. Enter a new character, Nia. Nia is chipper and optimistic, unlike Simon who is normally prone to moping and currently in full-blown self-destructive emo-vengeance mode.
Interestingly, Episode 9 is a departure in animation quality. The art largely lacks depth and detail, as though it were hastily put together for budgetary reasons. Gurren Lagann has done something similar back in Episode 4 when they handed over the reins to Osamu Kobayashi. The art style switch corresponded with a shift in the story from “Simon & Kamina discovering the surface” to “the Gurren-dan takes the fight to the beastmen.” I suspect that the change in artwork here was intentional, helping to provide a cognitive break between that which came before and that which is yet to come.
As for the significance of Nia having irises like a goat, I have no clue at this time. I’m sure if I dug deep enough I could find some symbolism there.