短语 child's play 用来形容非常容易做的一件事，小菜一碟，易如反掌。

例句

I finished the test very quickly. It was child's play!

Stop trying to fix the car and call a professional mechanic to do the job. This is not child's play.

请注意

另一个短语 a poster child 意思是一个典范人物。

Mr Cancino went from a poor young immigrant to a powerful businessman in a decade. He is a poster boy for the 'American Dream'.