If the statistics are to be believed, At World's End would be the most expensive film to be produced with a budget of $300 million.
Actor-Inspired Element: Jack Sparrow's way of talking and behaving was basically Johnny Depp adding to a character that was far more low-brow in concept.
Executive Meddling: Disney execs (and fans of the theme park ride) freaked out on reports that Depp was getting his teeth capped with numerous gold teeth and piercings for what was originally intended to be a "kid friendly, spooky" companion film to the now-forgotten Haunted Mansion movie. Depp's way of handling this was to take out the offending accessories when the Disney handlers complained... and then put them right back on as soon as they walked away.
Keith Richards as Jack Sparrow's dad? It seems to have a bit to do with the fact that Johnny Depp drew his primary inspiration for Jack Sparrow from Richards. So it was only natural that Richards would appear as the father of the character himself.
Will Turner isMakoto Itou (Making his role as Will extremely Hilarious in Hindsight if you know what happens with both Makoto and Will at the end of the respective stories: Resuming, Will gets his girl and ends in a nice ship as the captain, with his heart in a box; Makoto doesn't get the girl and he also ends in a NICE BOAT without being the captain of that boat... with only his head inside of it.)
Pragmatic Adaptation: On Stranger Tides is actually based on a book that by itself has no connection with the PotC franchise whatsoever.
Saved from Development Hell: Planning for the second film began in June 2004, but by November, the script was still not finished which forced Gore Verbinski to start planning some sequences without it. By January 2005 there was still no script, and with that on top of the rising costs for the film, Disney almost cancelled it. Around this time they started shooting...with the writers on hand, still writing the script. The same happened with the third film. Explains a lot, doesn't it?
What Could Have Been: Scenes were left out of At World's End which establish that, if the captain of the Flying Dutchman has someone to come home to at the end of his ten years, he can vacate the post to another. Leaving this scene on the cutting-room floor strips important Character Development from Tia Dalma, who knowingly condemned Davy Jones to a Fate Worse than Death by not waiting for him, and Jones himself, whose fury is now more sympathetic. It also downgrades The Stinger from full-on Babies Ever After to a Bittersweet Ending.
An entire game, Armada of the Damned was developed and nearly released, but for unknown reasons, was cancelled.