Some DVD's allow you to access clips while watching other clips. On 'The Matrix' DVD for example there is a 'Follow the White Rabbit' feature. Basically, while you are watching the movie a little rabbit appears in the corner of the screen - hitting Enter on your remote while the icon is present then takes you to a 'behind the scenes' featurette showing you how the scene you were just watching was acheived. At the end of the featurette the movie continues from where it left off.
Is there any capabitlity inside Encore CS3 to do this? If so, how is it acheived?