In Spanish there is a saying: dar gato por liebre.
It literally means to give a cat as a hare, as supposelly they have the same size and similar shape, and would be indistinguishable when cooked.
Albeit you probably should get some pieces to a veterinary in order to check the cat had no diseases (as supposely a rabbit in a butcher would have been tested for), and have guts to eat a pet.
A note on the saying
(Please, feel free to edit this answer and delete this note if you think it's off topic: this is an open collaborative site)
The saying means to trick someone, to deceive: it doesn't have a literal meaning. Culturally, in Spanish speaking countries eating a pet is disgusting. But the saying gives us (Spanish speakers) the idea that both meats would be indistinguishable and, so, be a propper introduction for the answer.