Question: how many episodes are in ben 10 alien force season 1
Answer: Season Episodes Originally aired First aired Last aired 13 April 18 , 2008 ( 2008 - 04 - 18 ) August 31 , 2008 ( 2008 - 08 - 31 ) 13 October 10 , 2008 ( 2008 - 10 - 10 ) March 27 , 2009 ( 2009 - 03 - 27 ) 20 September 11 , 2009 ( 2009 - 09 - 11 ) March 26 , 2010 ( 2010 - 03 - 26 ) Movie November 25 , 2009 ( 2009 - 11 - 25 )