When giving some kind of saying or folklore knowledge, in English we often say e.g.:
You know what they say? Two heads are better than one.
I want to say something similar in Chinese:
You know what they say? 天不怕地不怕,就怕老外说中国话!
I find this an amusing rhyme, and it usually gets a laugh. However, I'm not sure what to preface it with. YouDao uses semi-literal translations:
你知道他们说...
Nǐ zhīdào tāmen shuō...你知道他们怎么说...
Nǐ zhīdào tāmen zěnme shuō...
But I don't know if this is actually used by Chinese speakers (outside of translations from English). Perhaps it's Engnese (reverse Chinglish) to say this, and there's a more appropriate phrase in Chinese.
Question: How to phrase "You know what they say? [quote]" in Chinese?