3. "A House Divided," Dallas
Air Date: 3/21/80
You may not have ever seen a single episode of Dallas, yet there is simply no way you've watched anything else in the years since "A House Divided" aired without seeing a reference or 20 to the infamous, popular mystery of "Who Shot J.R.?"
The disgusting manner in which oil magnate J.R. Ewing (Larry Hagman, R.I.P.) conducted his business out of Southfork ranch gave just about every other cast member reasonable motive to cap the bastard. "A House Divided" can reasonably lay claim to jump-starting the concept of ending television seasons with cliff-hangers, but even if it didn't, the rabid fan and media response was a frenzy not seen over any other series then, and quite possibly to this date. The eight-month gap left the nation, and even Queen Elizabeth, with bated breath, leading to the theft (and subsequent return) of the season four premiere script from the production company offices.