| || Bye.
This character or achievement has been scrapped from the game. Not much info has been put on it but we do know, it's scrapped.
It it likely that this costume was considered for the Child due to his tendency to sneak around and hide in several of the cutscenes; however, this is simply speculation. It is confirmed that the Ninja would've been in a cutscene with the Pirate, but the story went elsewhere and slowly faded out of interest.