Aesop Fables Episode 13 THE CAT AND THE BIRDS

A Cat heard that the Birds in an aviary were ailing. So he got himself
up as a doctor, and, taking with him a set of the instruments proper
to his profession, presented himself at the door, and inquired after
the health of the Birds. "We shall do very well," they replied,
without letting him in, "when we've seen the last of you."
 A villain may disguise himself, but he will not deceive the wise.