Super Meat Boy Forever

To unlock Prototype Boy, you need to find 3 pacifiers.

You will know that there is a pacifier in a level by looking at the world map: if there is one in a level, a pacifier icon appears below the level's title, in grey if you didn't collect it yet, in colors if you did get it. If there is no icon, there is no pacifier (but a pacifier could be in the other version of the level -dark or light world).

If you see anything else I can add to this solution, please add a comment and I'll edit+credit you. Thanks!