 " Survival of the Fittest " was written by Weisman and directed by Cook . The episode originally aired on March 8 , 2008 , on the Kids WB ! block for The CW network . It had previously been shown to a packed audience at the 2008 WonderCon ; several goers were forced to stand and the creators and other members of the crew took the stage to answer questions . When Disney XD premiered the series , it aired the episode , along with the following two , " Interactions " and " Natural Selection , " on March 23 , 2009 . 
