Disc 1: Head into the Extra Features menu and proceed to play all the extras in turn. Once you have done this, move the cursor back to Concept/Animation Comparison and then press Right to highlight a Japanese symbol (see below). Select this to be presented with a 1m31s blooper reel featuring the English voice cast.
You can cheat a little if you don't want to watch the extras all the way through - just press the Menu button while one is playing and select the next feature from the menu. Note that once you have played the Egg you will need to go back to the main menu, come back to the extras, and replay all the featurettes before the symbol is available again.
All easter eggs were generously submitted by SirDonk