as merry as a cricket字面意思像蟋蟀一样快活，引申为非常快活；非常快乐；兴高采烈。

【例句】
Tom was as merry as a cricket when we saw him at Christmas.
圣诞节，我们见到汤姆时，他非常快活。

I think a charming girl should be as sound as a bell, as merry as a cricket and happy-go-lucky every day.
我认为魅力女生应该每天身体健康，开心快乐，无忧无虑。