Which episode of "Rick and Morty"  aired unannounced on April 1, 2017 and was replayed every half hour from 8pm to 12am ET, as part of Adult Swim's annual April Fools' prank?
Rick and Morty (season 3) The third season of the animated television series "Rick and Morty" originally aired in the United States on Cartoon Network's late night programming block, Adult Swim. It premiered with "The Rickshank Rickdemption," which aired unannounced on April 1, 2017 and was replayed every half hour from 8pm to 12am ET, as part of Adult Swim's annual April Fools' prank. The episode was also simulcast as a looping live stream on Adult Swim's site. The remaining episodes began airing on July 30, 2017. The season will feature a total of 10 episodes.
South Park (season 18) The eighteenth season of the American animated sitcom "South Park" premiered on Comedy Central on September 24, 2014 with "Go Fund Yourself", and ended with "#HappyHolograms" on December 10, 2014, with a total of ten episodes. The season featured serial elements and recurring story lines, which "The A.V. Club" noted as an experimentation with episode-to-episode continuity, in which the episodes "explore the consequences of the boys' actions [week to week], allowing the plots to be motivated in part by their attempts to dig themselves out of a hole".