It’s no longer just hip-hop sampling that rules in youth culture, but also jukebox musicals like “Jersey Boys” and “Rock of Ages,” and works like “The League of Extraordinary Gentlemen,” which features characters drawn from a host of classic adventures. Fan fiction and fan edits are thriving, as are karaoke contests, video games like Guitar Hero, and YouTube mash-ups of music and movie, television and visual images. These recyclings and post-modern experiments run the gamut in quality. Some, like Zachary Mason’s “Lost Books of the Odyssey,” are beautifully rendered works of art in their own right. Some, like J. J. Abram’s 2009 “Star Trek” film and Amy Heckerling’s 1995 “Clueless” (based on Jane Austen’s “Emma”) are inspired reinventions of classics. Some fan-made videos are extremely clever and inventive, and some, like a 3-D video version of Picasso’s “Guernica” posted on YouTube, are intriguing works that raise important and unsettling questions about art and appropriation.