When a man loves cats, I am his friend and comrade.

In an 1887 vignette titled “An Incident,” the narrator (Twain) encounters a young man carrying a gun and initially fears violence. He then worries the gun might be intended for a few shabby cats nearby, but learns the young man is actually trying to get food for the cats. Twain praises this kindness and says that anyone who loves cats earns his immediate camaraderie.

Twain uses affection for cats as a quick test of character: caring about cats signals empathy and decency, so he treats such a person as a trusted ally without needing any further social vetting.

Aha!—so far from being a madman, he was saner, you see, than the average of our race; for he had a warm spot in him for cats. When a man loves cats, I am his friend and comrade, without further introduction.