When Mulan is singing at her ancestors' grave, the characters on the tomb are actually the credits in ancient Chinese.
Hidden Mickey Mouse
The hidden Mickey can be found when the large Hun army is coming down the hill. As the army is running down there is a close of the army and then it pans out. When the view has panned out, in the clear area between the people in the army, is a Micky Mouse head. It will be near the center of the screen off towards the upper right.
In the scene where Mulan has just been honored as a hero and shes walking down the steps to go back home, on the railing of the steps are engraved mickey heads.