This was such an original concept that was carried out well by a combination of great actors/actresses, costume/makeup, and storyline/editing.
The FL and her ***sister trade off characters so unbelievably well. You can tell which character it is not by what they look like but their mannerisms ans facial expressions. honestly, a phenomenal acting feat.
I can honestly say that I have lost track of how many times I have watched it. It is also a great first chinese drama to start off with. kudos all around!