Harry Potter and the Goblet of Fire Easter Egg - Dobby and Winky!

Go to the scene in which Harry and his friends arrive at the campsite. After Ginny points her finger around and says "Look!", go frame by frame: you will see two house elves riding a llama. They pass on by very quickly, but you can definitely see them.
This is a reference to Dobby and Winky, two charcaters that were in the original book.