Quentin Tarantino’s ”Django Unchained” kicked off a marathon movie session in Hall H Saturday with a bang — a lot of bangs, really — including a spontaneous surge of appreciation from the nerd herd as The Weinstein Co. unspooled an eight-minute sizzle reel that lived up to its name.The big room was jammed in anticipation for Warner Bros. (”Man of Steel,” ”The Hobbit”), Legendary (”Pacific Rim”) and Marvel (”Iron Man 3”) panels; people who’d been waiting in line since 7 a.m. were still outside as the ”Django” panel got started. But Tarantino, Jamie Foxx, Don Johnson and Christoph Waltz made this one of the must-see panels of the weekend, carrying on a freewheeling conversation about history, movies and, in a few instances, ”Django Unchained.” Tarantino put on his history professor hat (it was really some kind of Bavarian wanderer’s lid), spending much of the time talking about the real conditions that faced blacks in the Antebellum South. ”It’s unimaginable to think of the pain and suffering that went on in this country. (the movie) can’t be any more fucked up than it actually was,” Tarantino said. Foxx, asked about how the movie’s racial themes would play, suggested that the level of discourse has elevated. And it helps to have the right director. ”I think we’re grown up,” said Foxx, still in his shooting beard and donning a black stingy brim fedora. ”We’re big boys and big girls. You expect Quentin to bow the walls off it. Just the script alone was blazing through Hollywood before it even began the process.” Foxx also outed the nickname of a Hollywood executive — ”Mr. No” — so called for his reputation for a quick rejection. ”I was just at a party and (Mr. No) was telling me ‘Aw man, I really wanted that script!”’ No word on his actual identity.