làn yú chōng shù
“to be included in a group just to fill a vacancy; to pretend to be an expert”
During the Warring States Period (475-221BC), the King of the State of Qi was very fond of listening to “yu” ensembles. He often got together 300 yu players to form a grand orchestra. The king treated his musicians very well. A man named Nanguo heard about that and he managed to become a member of the band, even though he could not play the instrument at all. Whenever the band played for the king, Nanguo just stood in the line and pretended to play. Nobody realized he wasn’t making any sound at all. As a result, he enjoyed his treatment just as the other musician did.
When the king died, his son, the new ruler, also loved the yu’s music. However, he preferred solos. He ordered all the musicians to play the yu one by one. Therefore, Nanguo had to run out of the palace.
The idiom “làn yú chōng shù” is used to mock someone who passes for a specialist in something. You can also hear people saying it about themselves to show their modesty.