If you set the system date on your console to Halloween (October 31) and then select the Easy, Normal, or Hard difficulty setting you will unlock this bonus. The Halloween bonus features creatures that have about a 20% chance of appearing with a jack-o-lantern on their head and it will also increase the difficulty of those creatures by making them immune to sunlight. The enemies affected by this are usually zombies, skeletons, wither skeletons, baby zombies, zombie pigmen, and baby zombie pigmen.
Unlock 'Dog' Song:
If you play the 'Cat' music disc in a jukebox and allow it to continue after the end of the song a hidden song named 'Dog' will start to play.
Unlock Character Skins:
At the 'Main' menu enter the following codes to unlock the corresponding character skin.
Press L2, Down, Circle, Up, Up, Right.
Ender Man Skin
Press Up, Right, Triangle, L1, Square, Square.
Press Circle, Up, L1, Left, Triangle, X, Down, R1.
Zombie Pig Skin
Press L1, Circle, Left, X, Down, R2, Up, Triangle.
Press Left, Right, Down, X, Circle, Square, Up.
Fire Under Water?!?!
First find a pond that is 3 deep
2nd place netherack in the water
3rd place 2 ice blocks on top of the netherack
4th get flint and steel and quickly break the ice on top of the netherack and light it on fire.
5th wait until the ice melts and you have fire under-water!