Rat through the very heart of it, New York, New York

[snopes]

The Urban Legends Reference Pages (Snopes.com, font of truth and scourge of Internet twaddle) says this: "Rats ... are for the most part intelligent, quiet, clean, sociable and even affectionate." So saying you married one isn't actually an insult.

Snopes goes on to debunk the idea that any city has as many rats as people, dismissing such vividly creepy aphorisms as "You're never more than six feet away from a rat."

http://www.post-gazette.com/pg/10007/1026324-151.stm