Easter egg: On Disc 2, go to trailers, and select Theatrical Trailer #3. While the trailer is playing, input the following numbers in order (slowly): 5 6 5 3 7 (JOKER). The trailer will restart and show a modified version of the original trailer, with Joker scribbling all over it. This is a reference to the marketing campaign promoting the movie, as fans who completed the entire set of events were greeted with the third "The Dark Knight" trailer, modified by the Joker.
Easter egg: This Easter Egg is on the second page on the Extras DVD. At the bottom of the page, between the Setup and More buttons, a crown pops up. Clicking on it brings up the Easter Egg. It is called Monster Cam (it shows the scene underground in the How, when the Narnians come up and surprise the Telmarines). There is a camera put in one of the minotaur's heads.