Anduin Wrynn, son of King of Stormwind Varian Wrynn, went through a major growth spurt just in time for the Cataclysm expansion. The first screenshot is “Before”. It was taken on March 10, 2010.
This second screenshot is “After”. It was taken on November 30, 2010. The Cataclysm expansion was released on December 7, 2010, which means that Anduin Wrynn became a teenager right before the Cataclysm happened.