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Who shot J.R.? was a mass media-manufactured open question in 1980. In the CBS television series Dallas, the character of J.R. Ewing, played by Larry Hagman, was shot by an unknown assailant in the final scene of its 1979-1980 season, which aired on March 21, 1980 and was entitled A House Divided.
Viewers had to wait all summer, and most of the fall due to a Hollywood actors' strike, to learn whether J.R. would survive, and which of his many enemies was responsible.
During the summer of 1980, the question "Who shot J.R.?" was asked in everyday conversations across America and worldwide. T-shirts printed with such references as "Who Shot J.R.?" and "I Shot J.R.!" became common over the summer.
In Father Ted, unstable Craggy Islander Tom always wears an "I shot J.R." t-shirt (presumably over 15 years old by the show's 1996 debut).
http://en.wikipedia.org/wiki/Who_shot_J.R.%3F