The characters can be unblocked only by finishing the given level. In order to find them we need to complete the whole campaign.
Pay attention that many characters must be bought in the Port even after being unblocked. Most of them just wander in our headquarters. We run towards them and use the indicated button (default: B).
It is a good idea to unblock Blackbeard (description below) and use him to smash the tavern's door (in the left part of the Port, where we can find him). Many characters which you can buy will appear in that room, you only need to destroy the tables. On the wall you can find an interesting item - browser of graphic materials taken from the game.
In order to buy all the characters you need to have loads of money. Becoming rich will be easier with the multipliers which you will get for discovering and buying one of the Red Hats.
The characters who do not want to be bought must be challenged to a duel - attack them with your sword and fight. Unfortunately it is sometimes difficult and annoying as the opponents have the tendency to run away.
You can create your own character in the left part of the Port, behind the usual place where Blackbeard wanders. First you need to lift the bridge in front of the puddle - build a span using the golden elements. Then with a little help of a barrel lift up the bridge. Next you need another barrel to get on the other side of it and you need to activate the other mechanism (in front of the building, at a pier). Run inside and look for the way up - grab the two ropes simultaneously. 
Below you can find the list of the characters required to find all the hidden objects at each level. Treat it as a "dream team" for Free Play where you can collect points and minikit bottles.
- Dog - you can unblock it during one of the first levels. It can dig up the treasure and go through square passes in the walls.
- Jack Sparrow - he is with you almost from the very beginning. He can use the hook mechanism, activate switches with his sword and find treasure using his compass.
- Mr. Gibbs - you can unblock him during one of the first levels. He can repair broken elements (red, pulsating bricks).
- Marty - you can unblock him at the beginning of the campaign. He is equipped with a big shotgun which can destroy the silver bricks.
- Billy - you can unblock him in the middle of the campaign. Like every other pirate-ghost he is the Sea Walker and he can get through the seaweed.
- Tattoo Pirate - you can unblock him in the middle of the campaign. He is so strong that he can deal with every orange bar.
- Siren - you can unblock her in the last movie. She can break objects made of glass.
- Blackbeard - you can unblock him after completing the game. Then you need to find him in the port - he is in the left part which you can enter if you have gold bricks. He is behind the puddle on the left. To have him you need to duel him. He costs fortune (500 thousands!) but in return you will get the power the destroy red and black bricks.