At MJ's Face-R-Us enter Square to put in coupon codes.

Effect	Password
Unlock Maxime the games artist's friends skin	MAXIMEAMIS
Unlock the Mojang staff's skin	MOJANG
Unlock the PJ Fresh Phil skin	PJFP
Unlock the Polytron skin	POLYTRON
Unlock the Team Meat staff's skin	TEAMEAT
Unlocks the Anthony Carboni skin	CARBONI
Unlocks the DTOID staff's skin	DTOID
Unlocks the Electric Playground television host's skin	ELECPLAY
Unlocks the Epic Meal Time host's skin	EMT
Unlocks the Gaiijin (Bit.trip) staff's skin	GAIJIN