With Indiana Jones trilogy coming to Blu-ray, Paramount Pictures continued its celebration of the iconic character with a screening of “Raiders of the Lost Ark” on the lot Thursday night with Paramount chairman and CEO Brad Grey, Steven Spielberg and Harrison Ford introducing the film. Prior to the screening, the trio answered questions on the making of the film and its impact on the film business. Ford was an unannounced participant, who surprised attendees as he walked into the Paramount Theater while Grey and Spielberg were fielding questions. “People were ready for a hero that takes his lumps, gets scared and gets beat up,” Ford said of Indy’s enduring popularity. The screening hasn’t been the only way Paramount has celebrated “Raider’s” 30th anniversary. Studio announced that it will be extending its Imax run, now playing in more than 300 theaters nationwide.