Lu, 25, who shot to fame from after debuting in South Korean boy band EXO in 2012, posted a photo of himself and a postbox on the Bund in Shanghai on his Weibo account last Friday.
"It's Friday today, I was here, see you tomorrow," the pop star wrote.
Soon the postbox, the sole purpose of which prior to April 8 was to receive mails to be delivered, has become the latest tourist attraction in China's financial hub.
Some have called this act "crazy", and that the these young women fans could find something better to do rather than create a traffic jam in the middle of the night.
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On the other hand, many have praised the fans' good etiquettes, state-run China Daily reported.
A Sina Weibo user Youyouzi said: "I don't know what they are fussing about in the comments. The girls haven't caused any troubles to anyone. They wanted to line up, and it's none of your business."