Disney is kicking off the campaign for its sequel to the 1982 film Tron with a global viral effort.  MTV reports the studio just executed a viral campaign running in 25 cities around the world where participants were led on scavenger hunts.  The hunts led to an online site where Disney promoted exclusive IMAX events for the film in New York, LA, London, Toronto and Sydney.  The sold-out events are scheduled for this Saturday and Sunday.  MTV guesses Disney could be planning anything from first glimpses to a full screening, though the latter seems a stretch for a film not scheduled to bow until the holiday season.  Read more at MTV.