Kevin Kern replaced Aaron Tveit as Fiyero on November 11, 2008. Then, Aaron Tveit returned to the role on January 20, 2009. He then returned to the role on March 10, 2009, replacing Arron Tveit, and left on February 2, 2010 when Kevin Kern replaced him.
The Wonderful World of Wicked - Kevin Kern is Fiyero
Broadway.com interviews Kevin Kern