Lord Shen fights hand-to-hand with a martial arts style called Cai Li Fo, a Chinese martial art that normally uses a metal fan for defensive and distraction purpose. However, being a peacock, Lord Shen uses his large tail feathers for that purpose instead.
According to The Hollywood Reporter, screenwriter Charlie Kaufman did an uncredited polish on the script. Previously, he had noted in an interview that he saw Kung Fu Panda (2008) with his daughter, and was impressed by the film.
At the end of the movie, when Po is telling Mr. Ping that he found his "real" dad, there is a sign on the wall behind Mr. Ping. It has chopsticks and a yellow slash on a red background--and looks like a "generic" McDonald's Happy Meal box. (The lower chopstick gives the illusion of the characteristic fold.) McDonald's included toys for both the 1st movie and this one, so it makes sense for this to be an Easter Egg (aka "Hidden Mickey").
Even though its a fully 3D CGI animated film some 2D animation is featured, from the films opening, the flashback scenes Po has, and even just some of the ways a scene is filmed, the perspective of the characters coupled with the dynamic or balanced color "flattens" the 3D animation to form a hybrid between 3D and 2D, also a few shots such as the panning shot over the cites draws from both the way cities where portrayed in older epic films by using miniatures and models and how the early 2D Dreamworks films used CGI rendered cities and effects blended to resemble the 2D animation.