If you can look at a dog and not feel vicarious excitement and affection, you must be a cat.

The quip plays on a familiar cultural contrast: dogs as openly enthusiastic and affectionate, cats as more reserved and self-contained. By claiming that anyone unmoved by a dog’s exuberance “must be a cat,” the line humorously reframes emotional detachment as a kind of species mismatch rather than a moral failing. The phrase “vicarious excitement” suggests that dogs’ joy is contagious—an invitation to empathy and shared feeling. As a light epigram, it also flatters dog-lovers by implying their responsiveness is the normal, warm-blooded human reaction, while gently teasing those who don’t share it.