It has already been said, but the NYC music scene is comprised of a whole lot of copy-ers. Some of them are very good, some of them are very bad. Some of them have not necessarily copied, but used other bands as springboards to build from (like Interpol, for example). The Strokes have been copied countless times, and everyone has jumped in on the dance/punk craze (not that it's a bad thing -- I like dance/punk).
But I have never seen a band that seems to have directly copied the Yeah Yeah Yeahs. The Grates have done just that. They are, like the YYY, a three-piece band consisting of a guitarist, drummer, a sexy singer. But did I say they were bad? Nope. They are good! Listen to some MP3s on their media player.
Yes -- I was unnecessarily harsh on the Grates, so forgive me. I love the YYY, and I love that sound. And yes, the Grates are a little different. Sometimes they use the guitarist as a back-up vocalist, but still, they keep the chaotic sound that is so closely associated with the YYY. And did I already tell you that I also love the singer?