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: (Blu-ray) On Disk 1, open the "Extras" submenu and highlight "BD-Live". Press the Right arrow/button and a wire-frame of Iron Man will appear below it. Press the Enter button and a brief behind-the-scene vignette between Stan Lee and Robert Downey Jr. will appear.
Easter egg: Go to the page for scenes 13-16. After you wait for a while,(Note: a lot of patience is required to find this) a 17th scene will appear. Click on it and it will take you to a page with secret military files. Unfortunately, only three of them actually work. Only time will tell how to access the other ones.
Easter egg: This Easter Egg is on the third page on the Extras DVD (the last page). Just click on the lion's head, and the Easter Egg comes up. This Easter Egg is about K.C. Hodenfield (he's the First Assistant Director and also co-producer).
Easter egg: On the "Bonus Disk", press the down button and a "Code Of The Fraternity" menu option will appear. Press the Select/Enter button and enter the code "01010111" (binary code for "W") to watch a behind-the-scene video.