This article discusses 21 things that should never be done to a cat, with the third one being especially concerning. Some of the things to avoid include giving human medication, using essential oils around the cat, punishing or yelling at the cat, declawing, leaving the cat alone for extended periods, and using a dirty litter box. The third thing on the list, which is considered the worst, is giving the cat human food that is toxic to them, such as chocolate, grapes, onions, or garlic. The article emphasizes the importance of being aware of the specific needs and sensitivities of cats in order to provide them with a safe and healthy environment. Following these guidelines can help ensure the well-being and happiness of your feline friend.