Remember back in April when Katy Perry was first playing New York at Mercury Lounge and was a fairly unknown name? A lot has changed since then, but then again two #1 singles, a huge album, and headlining the Warped Tour could do that to an act. One of music’s biggest rookies for 2008 will perform back to back nights at Irving Plaza (The Fillmore) on 04.07.09 & 04.08.09. Tickets are $18 and go on-sale today.  If you plan on going get them now, this will be a fast sell out.