There are many sub-stories in JY's canon. Many of them told by someone to someone orally. Those mini sub-stories usually tie up loose ends and discuss interesting story connected to the main plot. It doesn't deal with details but very smooth one breath story telling.
Nine Yin Manual Story - Told by ZBT to GJ
Origin of The Little Dragon - Told by QCJ to GJ
Mandarin Duck Story - Told by YD to GJ, HR and others
Heaven Sword Dragon Sabre True Story - Told by MJ shitai to ZZR
Cruel Husband and Wife - Told by QQC to YG and Gongsun Lu'e
Story of Mei Ruohua - Thought by Mei Chaofeng
and of course many others.
What other stories were presented in the novel?