Fifteen years ago this week, director Mike Mitchell's Sky High had a bit of a problem finding an audience, and like most problems facing cinema and society in general, this one was at least a little bit Johnny Depp's fault. The film opened the same month as Tim Burton's Charlie and the Chocolate Factory, which child-murdered its way to the fifth-highest opening weekend of the year and remained at #1 for weeks afterward. As such, Sky High had to take as "cult" a route as any Disney movie can. It took a few years of …