It is very odd that a cat with such unfriendly personality became friends with the dog right away. Usually, the introduction of a new pet takes time. Cats don’t always get along with dogs, because of dogs’ hunting instincts and the misinterpretation of body language. For example, a dog raising his paw to a cat may mean he wants to play, but a cat can take it as a sign of an attack, and starts hissing and might even scratch. Pudditat, probably, didn’t feel threatened, because the dog was so old and tired. Friendships take time to develop. If you got a new pet, and want him to get along with other pets in the house, let them get used to each other from afar. Separate the animals during mealtime. If you are leaving the house, try to separate the dog from the cat with a baby gate, to allow the animals sniff each other without coming into full contact. Regardless, it’s important to give equal amounts of attention to all your pets so no one feels left out.