SPOILER Link shared by @Lynn on Cheng Ling's lines dubbed over the original lines vs what the original lines were being said in the Special ending.

https://manggaetteokkie.tumblr.com/post/646677760420478976/broadcast-version

I love this explanation so much. It fits their personality and the end of novel well. Thank you for sharing. 

Thanks for sharing. The blog has so much amazing theories and explanations, I couldn't help feeling more appreciative for this drama T__T

Thanks you so much for sharing <3
So I can rest well now,. :')