乘龍快婿

Etymology
Based on the legend of Xiao Shi (萧史) and Nongyu (弄玉), the son-in-law and daughter of Duke Mu of Qin (秦穆公, r. 659 BC-621 BC, during China's Spring and Autumn Period. According to the legend, after the couple had retired to the seclusion of the middle peak of Mount Hua, one day Nongyu took her jade sheng (mouth organ) and mounted a colorful phoenix, and Xiao Shi took his jade xiao (vertical flute) and stepped onto a golden dragon.  For a time, the dragon and the phoenix flew into the air.  People at that time referred to Xiao Shi as "dragon-riding son-in-law," and this expression has evolved into a modern-day Chinese chengyu with the implied meaning of "ideal son-in-law."

Idiom

 * 1) ideal or excellent son-in-law