The beginning (the operation for a blind girl to see again) and the end of the film are based on true stories the Pang brothers read about in the news.
The dark/black figure/person that constantly appears in the film when the characters die is the Daoist (Chinese religion) form of the Grim Reaper. In Daoist belief, there are two Grim Reapers, the White and Black "Wu Chang". The Black Reaper is the one that escorts the newly dead to the "other world" of "afterlife".
When Dr Wah and Mun are on the train together, a ghostly woman's face appears in the train window behind them as they travel through a tunnel.
The movie was remade as "Naina" in hindi in year 2005