Without any spoilers, Tommen Baratheon (younger brother of King Joffrey) is likely to have a more prominent role in the next season of Game of Thrones. He has three cats, Lady Whiskers, Ser Pounce, and Boots. Lady Whiskers quickly establishes herself as the dominant cat of the group, stealing a mouse that Ser Pounce caught. This prompts Queen Cersei to tell Tommen: "Ser Pounce must learn to defend his right. In this world the weak are always the victims of the strong." (A Feast for Crows, Chapter 39)

Tardar Sauce, commonly known as Grumpy Cat, is an internet phenomenon, and draws huge crowds at appearances at major events like South by Southwest. She is already the subject of a small merchandising empire, so a jump into cat acting seems like the nest step. In her Grumpy Cat persona, she has the right look for a Lannister cat, and seems like the sort of pet that would attract Cersei's respect.