bad penny的用法和樣例：
例句
- At every party, Helen attended that year he'd keep coming back again like a bad penny.
那一年，海倫參加晚會，沒有一次不見到他，覺得很討厭。 - The conditioned response, once it is firmly established, can be extinguished dozens of times, but it will always return, like the proverbial bad penny.
條件反射一經形成，雖然可以一次又一次地壓制下去，但是它總會重新再現，真是擺也擺不脫扔也扔不掉。 - He kept turning up like a bad penny at every party.
沒有哪次晚會見不到他，真令人討厭。
