FWIW, "Wherefore art thou?" actually means "Why are you?" or more to the point "For what purpose?" which is the question Juliet asked because Romeo was from the Montague family which had a blood feud with the Capulets (Juliet's family).
She could have simply asked "Why art thou Romeo?", but it definitely isn't as poetic.
So the answer to "Wherefore art thou, Meowzer?" is because she likes cats...