Shishi (or Jade Lion) is a Chinese Lion made of green stone called jade.
Night at the Museum
It was one of the statues in the Museum of Natural History where Buddha points at Larry and the Jade Lion looks at Larry.
The Jade Lion is also seen with some Chinese Terracotta Soldiers watching the Eastern Island Head when his gum popped.
As the exhibits are fighting, the Jade Lion is also seen walking towards the basement. The Jade Lion is seen outside where it was summoned back to the Museum of Natural History with the others statues.
Battle of the Smithsonian video game
It doesn't appear in the second film, but it does appear in the DS game where they are enemies. Like the Stegosaurus, it has heavy armor on the front and needs to be attacked from behind.