Behind the Scenes:
Insert the second disc of the DVD set and on the "Main Menu" highlight the menu entry 'Interviews'. Now press your Right button and the image of the dancers will disappear. Press your Enter button now and you'll have the chance to see 5-minutes worth of behind-the-scenes footage from the rehearsal and shooting of the movie's final dance scene.
Reported by: MarthaRomero

Interviews:
Back on the "Main Menu", select the 'Interviews' menu entry this time and in the following menu, highlight Kenny Ortega's name. Press the 'Left' arrow key on your remote now and the dancers will appear on the screen. Now press your Enter button and you'll get to see an on-location interview featurette with interviews of many of the principal cast members.
Reported by: MarthaRomero

Bonus Feature:
The third Easter Egg can be found by selecting the 'Music Videos' menu entry on the "Main Menu". On the following screen highlight the entry '(I've Had) The Time Of My Life' and then press your Left button. If you press your Enter button now you will get to view a featurette on the 60s coming back in style during the 80s.
Reported by: MarthaRomero