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.
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.
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").