AS anyone who has seen the box-office phenomenon “Harry Potter and the Half-Blood Prince” surely noticed, the movie’s main characters have grown up. And so has its audience: many of those who are streaming to theaters are in their 20s.

The sixth film in the series was released almost a dozen years after the book that started it all: “Harry Potter and the Sorcerer’s Stone.”

The generation that ignited Pottermania as preadolescent readers is approaching college graduation or entering the workplace, and they have kept alive this flame of their early adolescence.

Indie rock bands have sprung up inspired by their obsession, with names like Harry and the Potters, the Half Bloods, and Voldie and the Wiz Kidz, playing songs inspired by Potter lore.