Thousands of Chinese fans of Mandopop king Jay Chou (周杰倫) gathered on Sunday evening outside Shanghai Stadium before the final concert of the Taiwanese singer’s four-day run in the Chinese city.

A singer can be lost among a big team of backup dancers on stage, and there are other distractions like fancy lighting and elaborate stage props. Often, the view is blocked by other concert-goers.

Getting past concert security can be tough sometimes, as anyone who has been forced to dump water bottles or surrender even mildly pointy items can attest to. But some concertgoers at JJ Lin's recent ...