Revealing mistake: When the gallows, in the Fort's courtyard, blows up, just before the huge explosion, four of the platform legs can be seen exploding in the same place, at the same time. A horse and rider pass by in the wide shot, another platform leg, the arm of the gallows and the actual platform explode in sync. Also, in the next close-up we see where the nearest leg of the platform has been cut to help facilitate the explosions impact. (00:31:25)
Revealing mistake: After the pirates open the gate on the Governor's property, they run towards the mansion and in the shot from behind they are casting shadows on the ground to their right. In the next shot from Elizabeth's window, they are casting long shadows directly in front of themselves. (00:31:55)
Revealing mistake: When the cannonball slams into the pirate at the Swann home, a wire visibly pulls on the back of his clothes and quickly propels him through the back doors. (Clearer in slow motion.) (00:33:15)
Revealing mistake: Koehler and Twig are with Jack in the prison when Koehler reaches for Jack's neck through the cell bars. In the first shot, the ray of moonlight is outside of the cell bars, over Jack's head, so Koehler's arm becomes skeletal while still outside the bars and we see the 'cursed' sleeve till the elbow. However, in the next shot, the ray of moonlight is only inside the cell where Koehler reaches, so Koehler's arm and sleeve are normal until it becomes skeletal, just when it's inside the cell. (00:37:00)
Revealing mistake: Right after Jack and Will commandeer the Interceptor and are moving away and Commodore Norrington climbs the stairs and says, "Just get them in range of the long nines," you can see a jet contrail in the sky behind him. (00:47:45)
Revealing mistake: In the scene where Jack and Will have just taken the Interceptor and the Dauntless is coming about, the men on the row boat get caught in its path. A second after the men abandon ship, you see the boat get destroyed. If you look closely at the forward wake of the ship, the boat is too far away to be destroyed by the front of the ship. And since the boat initially goes down when it's struck, it can't be the keel of the ship, since that would send it up. (00:48:05)
Revealing mistake: When Will hangs on the boom over the water, Jack says, "I can't bring this ship into Tortuga all by me onesy.." Then he brings the boom back and Will falls. While Will lies on the deck, in both shots, a band on the bottom of the right leg of his breeches is seen above his leg hose, whereas in the previous shot when he was falling from the boom, the band in not there. (00:50:10)
Revealing mistake: When Elizabeth first sees the skeletal pirates she stumbles backward, and when she lands on the tarp in the close-up, the flesh-covered thumb and part of a hand is visible behind her, at the top right, though the pirates are in skeletal form. (00:59:05)
Revealing mistake: Keira's stunt double Sonia is obvious in different shots throughout the film. When Elizabeth walks onto the deck of the Pearl, only to see the skeletal pirates, she stumbles backward and lands on the tarp, and it's very apparent that the one who comes back down from mid-air onto the tarp and goes back up is Sonia. Later on Isla de Muerta, Elizabeth whacks Jacoby (burning beard) with the gold rod and soon after she approaches a second pirate. This pirate is very pleased with himself when he takes the gold bowl off his head, and we can then see it is Sonia actually whacking him, but in the very next shot it is Keira reacting to whacking the guy. (00:59:05 - 02:00:05)
Revealing mistake: On the way to Isla de Muerta aboard Interceptor, during the storm there is a close-up of Jack's hand holding the compass. There are many other close-ups of Jack's hand in the movie, but in this particular close-up, it is not Johnny Depp's hand holding the compass. Depp's fingers are slim and normal looking, but in this close-up Jack's thumb is stout and has a severely enlarged/deformed metacarpal at the base of the thumb joint (likely arthritis). (01:03:35)
Revealing mistake: On their way to Isla de Muerta aboard Interceptor, Will and Gibbs discuss Jack and his history. Seen to the left of Gibbs are some of the crew looking out while standing at the ship's rail. It is obvious in some of these shots that the background is edited, the crew have the distinguishable blue screen ring around their bodies. (01:05:50)
Revealing mistake: The medallion's necklace has very narrow bar links, with one loop link at the end and it's not adjustable at all. When Elizabeth wears it in some shots, the necklace hangs much shorter, for example during her failed blood ritual. As the medallion falls into the Aztec chest during Elizabeth's ritual, the chain is even shorter. In other scenes it's long enough to tuck into her bodice as in a later scene aboard Interceptor with Will, when she gives him the medallion. When Will wears it, it's again much shorter, which can not be excused because he has a man's neck. The clasp closure is seen intact and it's not adjustable. It's simply a few different length necklaces used. The necklace gets ripped off, but that's also not an excuse for the length difference because as noted in another mistake the type of closure it has makes that impossible to do. (01:11:15 - 01:18:20)
Revealing mistake: In the close-up of Barbossa cutting Elizabeth's hand, we see as the blade goes across Elizabeth's palm, leaving an obvious thin red line where the blade sliced, but not leaving blood on the blade as it slices. The creases in her palm are also unaffected by the 'cut' that's being made. Yet when Barbossa holds the blade up to his face, the blade now has a good amount of blood on both sides. (01:12:00)
Revealing mistake: The clasp closure on the medallion's chain is NOT the sort that just comes apart when yanked on, evident in the many close-ups of the clasp throughout the film. Yet there are a number of scenes in which the chain is just pulled and it comes off easily: Elizabeth pulls it off aboard the Pearl, to barter with; Barbossa pulls it off, during her blood ritual; Elizabeth pulls it off to give to Will, aboard the Interceptor... The chain was secured to her neck with sellotape, in order for it to come off quickly for the shots. (01:12:15 - 01:19:28)
Revealing mistake: During the first blood ritual and other moments in the film, you can tell that Geoffrey Rush's (Barbossa) eyes are yellowish only because he's wearing colored contact lenses. (01:12:45)
Revealing mistake: When Barbossa cuts Elizabeth's hand her nails are short. When Will rescues an unconscious Elizabeth at the cave, she reaches for the medallion and her nails are longer. When Will ties the cloth around Elizabeth's hand and she gives him the medallion, her nails are short. However, when Jack says, "Ahh, where's dear William?" her nails are now manicured and much longer. Once she's marooned on the island her nails are short again. Most scenes were filmed out of sequence, hence the difference in nail length. Her nails should have been kept the same short length for the duration of filming. (01:18:35 - 01:29:10)
Revealing mistake: In the wide shot of the Black Pearl chasing the Interceptor, because of its sailing speed the flag at the stern of Interceptor is upright and blowing hard into the wind. Aboard the Pearl, when Barbossa looks straight ahead at the 'speeding' Interceptor, the flag is down and not blowing at all. (01:22:55)
Revealing mistake: After Barbossa shouts, "They're clubhauling," in the wide shot of Interceptor, the seven men on deck are very obviously not Jack's crew. Even the one dressed as Will does not look like him. (01:24:50)
Revealing mistake: When Pintel and Ragetti are below deck with the cannon and hit with forks and other utensils from the Interceptor's canons, Pintel's eyes are seen. The yellow contact lenses that Lee Arenberg wears as Pintel are seen in this and other shots during the movie. (01:25:30)
Revealing mistake: Aboard the Pearl, just as Barbossa screams, "And the rest of you, bring me that medallion," seen to the upper right of the screen is a very apparant high cliffside. There are no cliffs, high or otherwise, where they are having the battle - they're in open water. (01:27:30)
Answer: The curse needs the blood of everybody who took a coin from the chest. All the other pirates have already contributed so, as the movie opens, the only blood needed is Will's, substituting for his father. During the finale of the movie, Jack takes a coin from the chest, adding himself to the curse, so his blood is now required as well as Will's.
Tailkinker ★
But I didn't see any blood on the coins, and none of the pirates cut themselves, even before Will became part of the mix.
Yes, the other pirates did cut themselves before Will came into it, off-screen. The lack of blood on the coins can simply be explained as most of it dripping to the bottom of the chest, it being washed away by storms blown into the cave, or by the fact that they didn't drop that much blood on it in the first place.
When they had Elizabeth they believed she was Bill Turner's daughter, but they all thought the curse had failed, none of them had cut themselves so it makes zero sense.
They had been collecting back the coins for years. During that time they repaid their own blood. All they needed was the last coin and the blood of Bill Turner to break the spell.
lionhead