Rather than a clip from the movie, this is just a humorous bit of backstory, or possibly a deleted scene, attached to a preview.
Warner Bros. has been sitting on the film adaptation rights to ElfQuest for a long time. They were close to actually making a movie, but now the rights have been acquired by independent filmmakers Stephanie Thorpe and Paula Rhodes. Who are they? They're the people who made this ElfQuest fan-short back in 2011.