Extras are kind of like cheats for this game. Each extra can be turned on by simply hitting the [start] button then selecting extras and hitting (A) to activate them.
This will obviously be easy after unlocking all extras. Blackbeard is required for 2 of the Red Hats in the port.
Refer to my guide for the Red Hats Location;
*By the way you have to play one level to get this achievement. You don't really even have to play through an entire level, just have them all turned on at the same time for a second and it'll unlock right away.