Naming an animal as a witch's accomplice was standard practice. It didn't end with the animal.
A familiar, in the theology behind the trials, was an imp or minor demon a witch kept as a servant — most often described in the shape of a cat, dog, or bird. Reporting a neighbor's animal as suspicious wasn't a fringe accusation; it was one of the most ordinary moves available to a frightened colonist, requiring no confrontation with a person at all.
Tituba, the first person to confess in the outbreak, gave courtroom testimony describing a red cat, a black dog, and a yellow bird as agents of the Devil who had pressured her into service. Her testimony was treated as credible, detailed evidence — not folklore, but a witness statement.
In Andover, a dog was formally accused of being a witch's familiar and killed on the spot as a suspected accomplice. Cotton Mather himself later wrote that the animal had very likely been innocent — one of the only acquittals the entire episode produced, and it went to a dog, posthumously.
The trap for a modern instinct is that naming an animal feels like a victimless move — no person is directly harmed, and you've demonstrated vigilance to a watching community. But a familiar implies an owner. The accusation was never really about the animal; it was a slower-burning way of pointing at whoever the animal belonged to, and the community rarely let it rest there for long.
The cat was never questioned. It still lost.