This question had nothing to do with Lu Xun. It was a common online meme. This joke originated from a novel called " How Many Flowers Have Fallen in My Dream ", which was written by a Chinese author. In the novel, the protagonist Xia Lin had a dream conversation with a mysterious woman. The woman told Xia Lin that she only wanted to sleep with him. After Xia Lin realized the woman's true identity, he decided to give up pursuing her because it was impossible to sleep with her. It was used to describe something that seemed impossible or to express a helpless emotion.