The actor played scheming oil baron J.R. Ewing in the legendary programme, which chronicled the glamorous life of a wealthy Texan family and the corrupt double-dealing of its business empire.
The show became a massive hit around the world, attracting global audiences of more than 100 million before ending its 13-year run in 1991.
During its peak in the mid-1980s, Romanian President Ceausescu agreed to allow the show to be broadcast in the then-Communist country in a bid to show his citizens the decadence of democratic nations - but Hagman is convinced the plan backfired and led to a revolution and Ceausescu's eventual execution.
He tells Australian newspaper the Fairfield City Champion, "Romania put on Dallas to try and show how corrupt the American system was and it ended up with them lining up Ceausescu, who was the dictator, and shooting him 500 times - they wanted all that stuff they didn't even know was out there.
"He let that show in to show how decadent we were and they said, 'Yeah, we want some of it.'"