How do you purchase the bad characters in LEGO: Pirates of the Caribbean?

In LEGO: Pirates of the Caribbean, how do you purchase any of the bad/evil characters, like Davy Jones, the hammerhead shark guy, etc.?

If you wait around long enough in the port, the bad guys eventually show up and start fighting. Unlike good characters, which you can purchase directly (hitting B on the Xbox 360 version), they don't show a way to purchase them, but they do show they are available for purchase.

Is there a character I unlock at some point who will allow me to buy them, or is there some other way?

In order to purchase an "enemy" character (bad guys if you're good, good guys if you're bad), you must first beat them senseless.

Attack the character long enough and, instead of breaking, they will become available for purchase with B just like a co-aligned character. Once you have one "evil" character, it's probably easier to switch to them before purchasing other bad guys, to avoid the fight.