One option would be to open up the movie with a party of adventurers already in the heart of a dungeon about to grab the treasure, when they are beset by its guardians, including a dragon... After some really over the top fighting and antics, it cuts to a tavern where a much shabbier and poorer looking version of the group is trying, unsuccesfully, to get a free round of drinks with their fabulous tale. And then the story begins...