On each movie disc, when the "Warning" screen is showing, hit the following buttons on your remote to gain access to a different menu:
Audio
2
12
Blooper Reel
Insert the bonus disc and go to [Video Games and Still Galleries]. From there press on your remote control:
11 (press enter)
3 (press enter)
8 (press enter)
This reel runs for over 4 minutes and features footage from all three films.
Hidden Trailer
Insert the bonus disc. From the [Main Menu], select the [Trailers and TV spots] option. Press 1138 on your remote. Where "trailer" once appeared, it should now say, "Revenge Trailer". Select it to reveal a hidden trailer for "Revenge of the Jedi" before it was renamed to "Return of the Jedi".