<P> The initial summer run was made up of twelve half - hour episodes with the three veteran players joined by a featured player, along with a different special guest for each episode who would play in some of the games . </P> <P> On July 29, 2013, The CW announced that it had renewed the show for a 24 - episode season, airing Fridays at 8 ET / PT starting March 21, 2014, due to solid ratings . Illness prevented Stiles from appearing in two season 10 episodes, the first Whose Line shows he had missed in nearly 20 years, dating back to the original British series . Frequent guest Greg Proops filled in for Stiles on these occasions . </P> <P> On July 18, 2014, The CW announced that the show will be returning for a 24 - episode eleventh season (and third season on The CW) which started airing on April 17, 2015 . On August 11, 2015 the series was renewed for a twelfth season (fourth on The CW) to start airing May 23, 2016 . On October 24, 2016 The CW renewed the show for a thirteenth season (fifth season on The CW) to start airing May 29, 2017 . </P> <P> Several of the performers, including the three regulars Brady, Mochrie and Stiles, had previously appeared in the original run of Whose Line in the UK; other performers who had made appearances in the British version are Greg Proops, Brad Sherwood, Chip Esten, Karen Maruyama and Josie Lawrence, as well as musician Laura Hall . Mochrie and Stiles have been regulars since the show started, whilst Brady became a regular from season 2 - 7, appearing as a recurring performer in seasons 1 and 8 . Mochrie is the only performer to have appeared in every episode of the US series of Whose Line?, appearing in all 302 episodes thus far . </P>

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