- Davey Jones and every member of his crew were completely CG?
All the actor wore was a gray suit with white dots all over it! 
- Part of Davey Jones' beard came from a cup?
The computer guys scanned a stained styrofoam cup, set it as a texture, and then photoshopped it on Davey's beard!
- The island where the three-way swordfight takes place is completely swallowed by water during high tide?
- Somebody randomly got the idea to paint eyes and a bug on Jonny Depp's face right before shooting the scenes for cannibal island?
- The entire cast and crew had to have shots before going to the place where the scenes from the cannibal island were shot?
- Cement roads were built all along the island to help the trucks carrying costumes, cameras, and other equipment get around easier?
- PotC 2 and 3 were filmed back to back?
- After a hurricane hit the island where the boats were being kept, only the main ones (Flying Dutchman, Black Pearl, etc.) survived?
- One of the shots that was hardest on the cast was the scene where some of the crew of the Black Pearl fall into a chasm filled with water?It took a lot of hard work to swim against the current, all the way to the place that one short scene was being shot! And guess who made it there first? The actor who plays Mr. Gibbs, and the actor who plays the mute crewman (the two oldest members of the cast)!
I'm sure all who bought the DVD knew these, but for those who didn't, or haven't seen that particular feature yet, it's pretty shocking.