"Cat got your tongue," "a taste of your own medicine" and "when pigs fly" are some commonly used English idioms. Each idiom is potentially sarcastic and refers to embarrassing or awkward speechlessness, receiving ill treatment in exchange for treating others badly and something that is unlikely to occur, respectively.
Other oft-used idioms in English include "a piece of cake," "kill two birds with one stone," "break a leg," "hit the nail on the head" and "get something off your chest." Respectively, these idioms indicate something that is easy to do or understand, addressing multiple problems simultaneously, another way to wish someone good luck, getting directly to the point of a matter and confessing or discussing a bothersome issue.
Idioms are typically not literal, although they sometimes refer to real things or events, such as "once in a blue moon," which means something that happens only once in a while. A blue moon is the third full moon in an astronomical season with four full moons. This phenomenon occurs approximately once every three years.
Similarly, the idiom "to play second fiddle" identifies someone who is in a subordinate role. The term is often pejorative, but an actual second fiddle or second violin in a string quartet, string orchestra or full orchestra is vital to the textural sonority of the whole. In many cases, the second violin must fill the shoes of the first violin as well as provide the melodic and rhythmic counterpoint that is essential to harmonic structure.