Enter the Creation Hall in the Village Map, then hold L and press X, Y, B, A(2) to unlock the Astronaut, Knight, Ninja Girl, Spartan, and Supergirl templates. If you entered the code correctly, you will hear a sound.
Collect the hidden Pirate Coin in all levels to unlock the three "?????" songs at the bottom of Isaac's item shop list. The songs are "Opening Credits", Mayor Rosa's "Light Of My Life", and the "Real Life" ending song.