In terms of Television I'd say Twin Peaks or Wiseguy. Both were serialized shows back in the late 80's and early 90's in an era when TV shows didn't do serialization. Every TV episode back then was supposed to be immediately accessible to anyone who had never seen a prior episode before but Wiseguy first and then Twin Peaks broke this mold by telling a continuous story. Its commonplace nowadays but back then it was ground breaking. This led to shows like The X-Files, Deep Space Nine, Buffy, and others that started in the 90's doing a mix of one off episodes and mythology episodes. Nowadays many shows are completely serialized but it started with Wiseguy and Twin Peaks.