Even though it happened out of the usual order, “High School Musical” has quickly managed to do what Disney behemoths from “The Little Mermaid” to “Beauty and the Beast” were bred to do — it’s pretty much taken over the world. In just 30 months, “High School Musical” has spawned a sequel and morphed into a stage musical, concert tour, ice tour, best-selling book series, video game, a reality TV series and, next, a theatrical film opening Oct. 24.