On both discs from the 2-disc set, go to the main menu and from there to the [Special Features] menu and highlight the [Main Menu] entry at the bottom of the screen. Now press the [Up] arrow key on your remote to highlight the bellybuttons of the Gingerbread Man. Press [Enter] now and you will get a [Shrek Fun Fact] – a little piece of trivia from the movie. Every time you select this hidden feature, a randomly selected Fun Fact comes up.
Another Easter Egg is hidden on the second disc of the set. From the main menu, go to the [Play] menu entry and press the [Up] arrow key to highlight the music note in the background. This is the same Karaoke from disc 1.