"That Darn Katz!", is the seventh episode of the sixth season of Futurama, and premiered on August 5, 2010.
Earth is invaded by a race of intelligent cats, and are adored by everyone, except Nibbler and Amy.
Amy, Fry, Bender, Kif, Leela, and Nibbler go out drinking the night before Amy's doctoral exam. While everyone else is dancing, Nibbler "breaks up" with Leela as her pet. Amy wakes up 10 minutes before the exam. She arrives very late and in her underwear. She explains that her thesis is a planetary ratchet that can use the Earth's rotational energy and create electric current. One of the professor's cat starts batting the wire and because of her allergy to cats, she drops her model, breaking. Her doctorate is denied. The cat follows the crew back home.
The cat is immediately loved by everyone except Amy who is allergic to them, and Nibbler who is jealous. He begins to regret his decision to stop being Leela's pet. However when they find that the cat has Leela under a hypnotic spell and all the crew members have their own cats and are also being controlled. Amy and Nibbler visit Professor Katz to find out more. They discover that he was never even alive! He was just a puppet adapted for control by a cat! They return to Planet Express and sneak into the basement to discover the hypnotized crew members have built Amy's planetary ratchet.
The main cat reveals that he and all the other cats can talk. He also tells of how his home planet's orbit has slowed making both sides of the planet unbearable. He also tells that the first cats landed on Earth to steal its rotational energy in Egypt in 3500 BC and became domesticated. After learning of Amy's device, he built it to transfer the rotational energy from the Pyramid of Giza they built when they landed. Nibbler tries to break the spell using his own cuteness but it doesn't work.
The cats stop the planet and send the energy to Thubian-9 (their home planet). They then evacuate the planet as one side begins to reach extreme heats and the other begins to freeze over. They try to spin the ratchet the other way but it doesn't work. Amy realizes that if they continue pushing forward they can restart Earth. They take back the planet's rotational energy and Earth starts turning again and Thubian-9 slows back down. However, the Earth is now spinning in the opposite direction! For saving Earth with her planetary ratchet, Amy is awarded her Ph.D. in Applied Physics. Nibbler apologizes to Leela and he returns to being her pet.