Liane Cartman hired "The Dog Whisperer" Cesar Millan in the South Park episode, "Tsst", to help train Eric Cartman. Unlike assorted nannies who were hired to discipline Cartman (all of whom were destroyed mentally or emotionally by him), Cesar's approach proves to be the most successful, as he treats Cartman like a dog, rather than a human being. Mrs. Cartman becomes so grateful for his help that she begins propositioning Cesar for a deeper relationship. When Cesar reminds her that he is merely there to teach her to control Cartman and then leaves, she back peddles on the training, causing Cartman to regress into his evil tendencies.
Unlike almost all celebrities that appeared on South Park, Cesar wasn't disrespected in anyway. In fact, he was shown in a very positive light has the only person able to manipulate and control Eric Cartman's behavior, to the point of causing him to temporarily behave like a rational human being.