The Thing
Easter Egg : Hidden Music Score
Go to the Bonus Materials from the main menu and there select the Terror Takes Shape documentary. Go to Language Selection and you will find an menu called Music Score. It's the entire music score for the film.

There's Something about Mary
Easter Egg : Hidden DVD Credits
You can go to highlight the scene select menu and hit the right arrow button and it will change the color of marys dress. It just brings up a credit screen for the makers of the DVD.

Three Kings
Easter Egg : A Variety of Hidden Features
1) A hidden TV Spot: go to the disc's 'Special Features' menu, then select 'Production Notes' and from there go to the 'Origins'. Here, push the arrow key up and you should find a highlighted grenade. Press 'Enter' and a menu appears with the TV spot on it. 2) Hidden passwords: To be used on the Three Kings DVD Events web-site (which isn't there yet). To get the first one , go to the 'Special Features' menu then select the 'Cast & Crew' menu. Here push the arrow key up and you should see another grenade highlighted. Press 'Enter' to obtain the password 'SCUD'. The second one can be found by going to the 'Special Features' menu, and choosing 'Continue' until you get to the final menu. There push the arrow key down until another grenade is highlighted. Press 'Enter' and you will be given another password, 'BAGHDAD'.

Toy Story 2 (3-pack supplemental disc)
Easter Egg : Hidden Joke Reel
Go into the "Music" menu within the "TS2" section of the supplemental features disc. While highlighting one of the song demos (I don't remember for sure, but I believe it's "When She Loved Me") arrow to the left to reveal a hidden question mark. Select it to view an alternate (joking) version of the end of the song sequence in the movie.