While filming in London in October 2010, Johnny Depp received a letter from a local 9-year old schoolgirl, telling him her classmates needed help to 'mutiny' against her teachers. He turned up with almost no warning at the school in full Sparrow outfit, but advised against mutiny.
Penélope Cruz was pregnant throughout production, but it wasn't noticeable until September 2010. As Penélope's baby bump grew, it caused difficulties in wardrobe, so the producers enlisted the help of Cruz's younger sister, Mónica Cruz. According to reports, Penélope filmed the close-up shots, while Mónica doubled for her in the long-distance scenes.
Jerry Bruckheimer gave strict instructions to casting directors that actresses auditioning for the mermaid roles must have natural breasts. During shooting of their scenes, they were not allowed outside until dusk in order to avoid spoiling their make-up.
After Walt Disney's chairman of 38 years, Dick Cook was fired, Johnny Depp talked to LA Times and said his enthusiasm for the fourth Pirates movie had reduced after Cook left the project. "There's a fissure, a crack in my enthusiasm at the moment," Depp said. "It was all born in that office." One of the reasons Johnny Depp committed to Pirates of the Caribbean: The Curse of the Black Pearl (2003) was because he trusted Cook, who supported him while "others at the studio were less than enthusiastic about my interpretation of the character, Dick was there from the first moment. He trusted me."
This was the first film to be released in the 4DX format in Mexico and in the Western Hemisphere, which is only available at select Cinépolis theaters. 4DX features strobe lights, tilting seats, blowing wind and fog and odor effects.
When making Pirates of the Caribbean: The Curse of the Black Pearl (2003)_, the scriptwriters revealed that they placed the story in a thirty-year environment set loosely between 1720 and 1750. They also said that they did not intend the films to be entirely historically accurate. However, it was revealed that Pirates of the Caribbean: On Stranger Tides takes place in 1750.
As Jack enters the Santiago, the camera flashes to a skeletal Ponce de Leon laying on a bed, surrounded by treasure. This is a reference to the Pirates of the Caribbean ride in Disneyland where guests see a skeletal pirate captain laying in bed, surrounded by treasure.
Oren Aviv said Disney had chosen to scale this movie down from the former in the series; "It's important to get the story right and it's important to me to scale it down, because we can't get bigger. The movies have subsequently gotten bigger and bigger and very complicated and they were satisfying on so many levels obviously, but I want to kind of reboot the whole thing and bring it down to its core, its essence, just characters." He agreed that there is a lot of Captain Jack Sparrow's back story that we haven't seen yet without confirming or denying that we might see some of that in the fourth movie
Blackbeard's ship, The Queen Anne's Revenge, is actually a modified version of The Black Pearl, one of the vital ships in the series. The Sunset, as it is called in real life, was used in the latter two parts of the first trilogy and in 2010 redesigned to portray the Queen Anne's Revenge in this installment. The biggest change was above deck. The back was cut off to deck level and rebuilt again in two stories.
The film budget had to be scaled down to no more than $200 million (the Pirates of the Caribbean: At World's End (2007) budget was close to $250 million). This was mandated by studio president Rich Ross (who replaced the fired Dick Cook) in addition to the then 2008 economic slowdown in the US.
Barbossa's ship, the Providence, was portrayed by the HMS Surprise, part of the collection of ships of the Maritime Museum of San Diego (www.sdmaritime.org), where it is open daily to Museum visitors. To sail the ship during the filming, Disney hired a crew from among volunteers and staff of the Maritime Museum. Surprise is a 179' full-rigged ship. She was built in Nova Scotia in 1970 from original Admiralty plans for the 1757 British 24-gun frigate HMS Rose, for which she was originally named. The ship was purchased in 2001 by 20th Century Fox and modified to serve as the HMS Surprise, under the command of fictional Captain Jack Aubrey (Russell Crowe) in the 2003 film Master and Commander: The Far Side of the World. The Maritime Museum of San Diego purchased the ship from Fox Studios in 2004, and retained her movie name. In both of her names the prefix "HMS" (meaning Her (or His) Majesty's Ship) is an honorary rather than an official designation, since she does not hold a royal warrant.
Blackbeard says that his quartermaster sees things before they happen. This is an oblique reference to the character of Fedallah in the novel Moby Dick, the source of various prophecies about the death of his captain.
When Phillip (Sam Claflin) is tied up to the mast, a pirate says to him, "Either you're with us or against us." - echoing former president George W. Bush's quote on the aftermath of the 9/11 terrorist attacks.
The trivia item below may give away important plot points.
The outdoor entrance to the Fountain of Youth is the Waikapala'e Wet Cave on the north shore of Kauai. Analogous to the film's magical watery passage to The Fountain of Youth, the cave holds a real submerged (depending on water level) passage through which explorers can travel in order to reach an isolated chamber known as "The Blue Room." Some Hawaiians tell of an actual pirate treasure found hidden in "The Blue Room" by the original discoverers. The pirate treasure (if it ever existed) is gone, but the cave and chamber remain a natural treasure, still accessible to intrepid explorers.