Pretty Scary Update

The Pretty Scary Update is a planned major update, labeled as 1.4.1, with an official release on Thursday, October 25, 2012. Among the main changes are a number of new mobs and variants, wearable and placeable heads, a new boss (the Wither), the command block, the anvil and the beacon.

Development on the Pretty Scary Update began directly following 1.3.2, which was released on August 16, 2012. 15 development snapshots for 1.4 from 12w32a to 12w42b were released. The 1.4 Pre-release was unveiled on October 19, 2012, so that modders can start preparing their mods before the launch on October 24, 2012. However, Mojang found a mob suffocation bug after this was released, and was forced to delay the launch by a day. The 1.4.1 Prerelease was unveiled on October 23, 2012.

The official name of the update was revealed at PAX Prime 2012 during the Minecraft panel, then later with snapshot 12w36a. Dinnerbone first revealed the 1.4 release date with Snapshot 12w40a, where he stated that he was fully into the "Prepare for release" mode.

The Pretty Scary Update was originally intended to include the Modding API, however this has been pushed to a later version.

Lighting bugs present in 1.3.2 were only partially fixed. Dinnerbone first introduced changes in snapshots 12w39a/b. Dinnerbone tweeted to revert back and push this to 1.5. Other changes postponed to a later version of Minecraft (most likely 1.5) including redstone changes, and rendering changes.

Features
Note: I just edited the Wiki. :3

General

 * Improved server list
 * Server IPs can now be hidden individually when editing or adding a server
 * Server version is now displayed left of the connection bars
 * Server ping tooltip now shows if the server and client have mismatching protocol versions
 * Mismatching servers can't be joined
 * Improved settings menu
 * Renamed Chat Settings to Multiplayer Settings
 * Added an option for cape-owners to hide their capes in-game
 * Added Fullscreen and VSync toggles
 * Improved F3 mode
 * The piechart is now shown when using shift+F3 instead of vice versa
 * Added the cardinal direction and the degree value to the f value indicating the direction the player is facing
 * Now shows which chunk and where in that chunk the player is in on X and Z values
 * Pressing while holding  will toggle the auto-pause when the Minecraft window loses focus
 * Pressing while holding   will toggle detailed item descriptions, which additionally show item id, damage value, color code, tool/armor/weapon damage and map zoom level and scale on the tooltip
 * Pressing while holding  will reload the texture pack
 * Updated language files

Gameplay

 * Improved Multiplayer
 * Spawn protection now is disabled if there's nothing in ops.txt
 * Spawn protection radius can now be changed in the server.properties file
 * Improved Creative inventory
 * Items can now be cloned by using Pick Block on them - An item stack with the highest amount of items possible in it will be created
 * Items can now be shift-clicked around on the survival inventory screen
 * Improved General inventory
 * Pressing the 1-9 hotkeys while hovering over an item will exchange that item with the one from the corresponding hotbar slot
 * Status effects now cause the inventory window to be off-center regardless of screen aspect ratio
 * Added & improved a few commands
 * Added  command to change difficulty
 * = peaceful
 * = easy
 * = normal
 * = hard
 * Toggling PvP
 * Added  to change your own or other players' spawnpoint to where you are standing or to specified coordinates
 *   
 * Added, an alias for
 * Added  to change the current weather and optionally set the duration for the new weather
 * Added   to look up and change gamerules regarding Command Block output
 * - Whether fire should spread
 * - Whether mobs should drop items
 * - Whether mobs should naturally spawn
 * - Whether blocks should have drops (does not work for paintings)
 * - Whether the player should keep items in their inventory if they die.
 * - Whether creepers, endermen and withers should be able to change blocks.
 * Added  to clear a specified player's entire inventory or remove only one block/item from it
 * Changed  so it can be used to give and take entire experience levels by appending "L" to the number
 * Changed  to work with relative coordinates
 * Added command target selectors
 * Available selectors:
 * - Closest player
 * - All players
 * - Random player
 * Can have arguments specified in  using the syntax , where   is the argument
 * Available arguments:
 * - Coordinates
 * - Range
 * - Minumum experience level
 * - Maximum experience level
 * - Minimum range
 * Special argument only usable with :
 * - the maximum count of players to return. Numbers below 0 will make it return the last x amount of entries
 * Updated the sound engine
 * Added sounds for placing Wood-, Stone-, Plant-, Sand- and Gravel-like blocks
 * Added sounds for walking on Sand, Gravel, Soulsand, Grass and Stone
 * Added sounds for zombies, skeletons, cows, pigs, spiders, endermen, ghasts, silverfish, magma cubes, wolves, the ender dragon, bats and the anvil.
 * Added sounds for curing a zombie, infecting a villager and a remedy sound.
 * Added sounds for setting things on fire and shearing sheep
 * Added sounds for climbing ladders and riding minecarts
 * Added a sound for levelling up which is played every 5 levels
 * Added constant noise to liquids
 * Improved Portals
 * Mobs, items and projectiles now pass through them, preserving momentum
 * Entities will pass through instantly, but at a longer "cooldown"
 * Portals will allow fire burning entities like blazes to leave the Nether and potentially burn things
 * Portals will teleport an entity relative to where it entered
 * Players are now positioned correctly when going through Nether Portals
 * Nether Portals are now instant for players in Creative mode
 * Improved Adventure mode
 * Blocks can now be mined with the proper tools
 * Blocks can now be placed
 * Improved Breeding
 * Chickens now use seeds instead of wheat to breed
 * Pigs now use carrots instead of wheat to breed
 * You can now restore a desolate village or create a completely new village
 * Added & changed many minor things
 * Added Boss Names above boss health bars
 * Experience is now awarded for fishing and breeding
 * Worlds can now be re-created from the world selection screen
 * Changed many items, improving item icon style to be more consistent
 * Items spawned using  are picked up almost instantly now
 * Doors, trapdoors, levers and buttons are no longer triggerable with the left mouse button
 * Added an NBT tag for items to have lores
 * Added an NBT tag for mobs to decide whether they can despawn
 * Fixed many bugs
 * Fixed  command only working for ops
 * Fixed  not working correctly
 * Partially cured lighting glitches
 * Fixed held items being colored when wearing tinted blocks/armor
 * Fixed the second layer on skins not being placed correctly when sneaking
 * Blazes now properly spawn in Nether Fortresses
 * Fixed pets teleporting around randomly
 * Fixed pvp-disabled servers still allowing players to set other players on fire using Fire Aspect enchanted swords
 * Fixed entities in minecarts becoming invisible
 * Fixed mobs randomly suffocating
 * Fixed stairs, slabs & fences glitching visually sometimes
 * Fixed mobs falling through blocks
 * Fixed wet wolves looking way too scary
 * Fixed wet wolves looking way too scary

World Generation

 * Customizable World generation
 * Made superflat worlds customizable
 * Are now made up of layers specified with block id, data value and height
 * Biome can now be changed
 * All generation settings are stored in a preset, which can be shared and re-used
 * Terrain can now be decorated and structures other than villages can spawn
 * Default presets:
 * Classic Flat -
 * Tunnelers' Dream -
 * Water World -
 * Overworld -
 * Snowy Kingdom -
 * Bottomless Pit -
 * Desert -
 * Redstone Ready -
 * Preset format with example: 95;35:2;2x20;1;stronghold – 95 is the format version, followed by a semicolon and the layer information. Every new layer is separated by a comma and must consist of the block id and can additionally have   appended to specify   as the data value. Before that, you can put   to specify that this layer should be put   times. After a semicolon follows the biome id. After another semicolon follow all structures to be generated, including their options.
 * Added Witch Huts in swamps
 * Silverfish blocks now rarely generate in Extreme Hills biomes
 * On average, nearly one Silverfish block is generated per Extreme Hills chunk
 * Carrots and potatoes can now be found growing in villages 

Blocks & Items

 * Command blocks
 * Runs editable commands when triggered by redstone
 * Intended for adventure maps
 * Can only be edited by OPs, as long as  in server.properties is enabled
 * Only obtainable using
 * Can operate in silent mode where it doesn't display commands in the chat box.
 * Beacons
 * Intended as an endgame block
 * Continuously glows and gives a selected status effect to players within 16 blocks while beaming a beacon of light directly upwards (as bright as glowstone)
 * Activated by building a solid pyramid of iron/gold/emerald/diamond blocks underneath and selecting an effect
 * The cheapest configuration requires 9 blocks, while the best configuration requires 164 blocks
 * Has to be directly exposed to skylight to work
 * Building square platforms of increasing size and the same material per layer will activate it and increase range and status effect selection
 * Viable materials are iron, gold, diamond and emerald blocks
 * Changing selected status effects costs 1 emerald, diamond, gold ingot or iron ingot
 * Unlockable effects, with increasing amount of required layers of blocks required:
 * Speed and Haste
 * Resistance and Jump Boost
 * Strength
 * When all 4 layers of blocks underneath are built correctly, a second status effect can be chosen
 * This second status effect is Regeneration or tier II of the previously chosen effect
 * Effects given by the Beacon will have less intrusive particles than others on the screen, such as those of potions
 * Anvils
 * Used for repairing and combining enchanted items as well as for renaming any item/block for experience levels
 * Tools can also be repaired using one piece of their material
 * Enchantments that are the same are upgraded by one level as long as they are both the same level and the higher level exists
 * Conflicting enchantments will be removed and only the first one will be kept
 * Becomes damaged from using and dropping it - Damage persists in inventory and splits up into 3 categories: Anvil, Slightly Damaged Anvil & Very Damaged Anvil
 * Can be placed in 4 orientations, but can't be moved by pistons
 * Experience level cost depends on enchantment levels & rarities, whether the item will be renamed and whether the item has been used with an anvil before - Maximum experience level cost is 39 levels, unless in Creative mode
 * For a more detailed explanation on how enchantments are combined using the anvil, see the Anvil mechanics page
 * Is affected by gravity and does 1 heart of damage to mobs and players it falls on per block it fell, excluding the first one - Players killed by a falling anvil cause the death message "Player was squashed by a falling anvil" to appear in chat
 * Certain blocks are destroyed when an anvil falls on them: levers, buttons, torches, redstone torches, redstone repeaters, flower pots, rails & mob heads
 * Mob Spawners
 * Added a few NBT tags to change a few key spawning rules
 * Range can now be changed
 * Maximum amount of spawned entities within spawning range can now be changed
 * Horizontal spawning radius can now be changed
 * Spawned mobs can wear and carry any items and blocks as well as have a custom drop rate of held items
 * Added an NBT tag for mobs to decide whether they can despawn
 * Added an NBT tag for mobs to decide whether they are invincible
 * Repeaters
 * Can now be locked by powering their sides with another repeater
 * When locked, they show a little bedrock barrier in place of the delay indicator torch and won't change their output signal
 * Flower Pots
 * Lets players plant all kinds of saplings, mushrooms, flowers, cacti, dead shrubs and ferns
 * Using pick block on it gives the potted plant
 * Right-click it with something to plant it, hit it to get both back
 * Cobblestone Walls
 * Available in cobblestone and moss stone variants
 * Behave like fences - Connect to each other, to other blocks and to fence gates & have a 1.5 blocks high collision box
 * Have a different, higher shape in corners and when blocks are placed on them
 * Wooden logs
 * Changed placement: Instead of facing the player, it will face the surface it is placed on
 * Place it on the side of a block to get a sideways log.
 * Place it on the top or bottom of a block to get a topside log.
 * Stairs
 * Now connect to other stairs to form corner stairs
 * Item Frames
 * All items and blocks can be framed
 * Clocks, compasses and maps function - Maps show only one marker, the frame itself
 * Mounted maps show markers on copies of that map
 * Using pick block on it gives the framed item/block, but only works in Creative
 * Paintings
 * Added Wither painting
 * Mob Heads
 * Are very rarely dropped when mobs are killed by players
 * Only drop from Wither Skeletons, but also exist for creepers, zombies, skeletons and players
 * Can be put on the ground in 16 orientations and hung on walls
 * Can be worn
 * Using external editors or mods player skulls can be assigned to specific players - They then have tooltip "Player's Head"
 * Add the NBT tag "SkullOwner" -> (player name) on the skull items.
 * Trapdoors
 * Can now be placed on the top half of blocks
 * Placement works similar to that of slabs and stairs
 * Buttons
 * Now stays active for 0.2 seconds longer
 * New crafting recipe – Only 1 stone block required
 * Wooden Buttons
 * Additionally can be activated by arrows
 * Requires 1 wooden plank to craft
 * Fire
 * Now spreads more aggressively depending on difficulty
 * Saplings
 * Decreased hitbox size
 * TNT
 * Is now triggered by flaming arrows
 * Potatoes
 * Can be planted on hydrated soil and drop 1-4 potatoes when fully grown
 * Can be grown instantly using bonemeal
 * Can be Smelted to receive a baked potato
 * Rarely drop poisoned potatoes
 * Potatoes give 0.5 hunger points, poisoned potatoes give 1 hunger point and have a chance to poison you, baked potatoes give 3 hunger points
 * Carrots
 * Can be planted on hydrated soil and drop 2-4 carrots when fully grown
 * Can be grown instantly using bonemeal
 * Can be crafted surrounded with 8 gold nuggets to get a golden carrot
 * Carrots give 2 hunger points, golden carrots give 3 hunger points
 * Carrot on a Stick
 * Used to control pigs
 * When held, it dictates the direction pigs players are riding will head in
 * Nearby pigs flock towards players holding it
 * Slowly loses durability when riding pigs
 * Pigs start slow but end up going about 5 blocks per second
 * Can be right-clicked to give the pig a short speed boost - This takes up a chunk of the durability
 * The pigs ‘eat’ the carrot eventually, leaving the player a fishing rod and will require another carrot to continue riding.
 * To craft, the carrot must be placed at a diagonal below the fishing rod
 * Pumpkin Pie
 * Restores 4 hunger points
 * The crafting recipe is shapeless: assemble a Pumpkin, Egg and Sugar into the crafting inventory
 * Nether Star
 * Drops from Withers
 * Used to craft the Beacon
 * Glows like an enchanted item
 * Night Vision Potion
 * Brewed by adding a Golden Carrot to an Awkward Potion
 * Invisibility Potion
 * Effect now hides the nametag and cape
 * Mobs only attack you when you walk into them or attack them
 * Splash potions of invisibility can also make mobs partially invisible, although eyes of some mobs still show
 * Brewed by adding a Fermented Spider Eye to a Potion of Night Vision
 * Potions
 * Can now have any available potion effects, level and duration
 * Data are saved using NBT tags, but potions retain their original color
 * Maps
 * Are now crafted as an Empty Map and will become a real map by right-clicking
 * Start out at their closest zoom level and can be extended by adding more paper
 * Players see other players moving around on the same map
 * Craft an existing map with an empty map to receive an extra copy of the map
 * Removed text overlay
 * Are labelled 'Map #0' and so on
 * Now align to a grid and can be stacked to 64
 * When outside a map's range, the player is displayed as a small circle at the edge
 * Armor
 * Diamond Armor sleeves now have a notch on the inner side
 * Completely revamped leather armor
 * Leather Armor
 * Can now be dyed in 16,777,216 potential different colors
 * Putting it in a crafting grid with dyes applies all colors
 * Dyed armor's tooltip will display ‘’Dyed’’
 * Right-click dyed armor on cauldrons to wash it and remove some water from the cauldron
 * Changed item and model color and texture
 * Now uses two overlayed textures, one being the color

Mobs

 * Wither
 * Three-headed flying player-created boss mob shooting projectiles at mobs that are not undead and players
 * Place 4 pieces of Soulsand in a T-shape and place 3 Wither Skeleton Skulls on top to summon it
 * After spawning, it flashes blue, builds up health, grows slightly and is invincible for a few seconds - Then it explodes and starts attacking players and mobs
 * Each head can fire projectiles, so called Wither Skulls, at different targets - Projectiles explode on impact
 * Shoots two kinds of projectile - a blue one from the little heads, targeting mobs and a dark one from the big head targeting players
 * When hit by projectiles, players get the ‘’Wither II’’ effect, which acts like a slower poison effect that can kill and turns affected players' health bars' hearts black
 * Constantly regenerates health
 * Gains Wither armor when taken down to half health, making it immune to arrows
 * Drops a Nether Star when killed
 * Darkens the sky when spawned in the Overworld
 * Wither Skeletons
 * Carry and rarely drop Stone swords when killed by players
 * Drop bones, coal, and rarely wither skulls
 * Give players Wither effect when hitting them
 * Spawn in Nether Fortresses
 * Will now rarely, depending on difficulty, spawn with the ability to pick up armor, head wear, items, blocks, weapons and tools - Armor and tools & swords are equipped automatically and will be exchanged for better gear when possible        - Items that are picked up will have a 100% chance of dropping after dying - When killed, they drop what they are holding
 * All equipped gear is functional - Swords and tools do more damage on attacks, armor protects the mob
 * Rare tool drops now are damaged when it drops
 * More advanced gear is more likely to spawn with mobs when playing on harder difficulties and rarely drops when the mob is killed by players
 * Witch
 * Looks like an offshoot villager
 * Throws splash potions of poison, slowness, weakness and instant damage at players
 * Holds a potion and wiggles its magical nose with a wart on it when attacking
 * Has a hat, which sometimes emits particles
 * Regenerates health over time
 * Drinks potions of instant health and fire resistance to defend themselves in combat
 * Is immune to 80% of splash potions' effects
 * Drops Sticks, Glowstone, Redstone, Gunpowder, Sugar, Spider Eyes, Empty Bottles & Water Bottles when killed
 * Has a chance to drop the potion it is holding if killed by players
 * Spawn in Witch Huts in swamps
 * Bats
 * Hang on the ceiling when idle, starts flying when players come near
 * Spawn in dark caves
 * Sleep at day
 * Don't trigger pressure plates or tripwire
 * Tamed wolves
 * Their collars can now be dyed by right-clicking the wolf with dye
 * Iron Golems
 * Now attack creepers, Slimes and Magma Cubes
 * All hostile mobs
 * Will now jump down to players as long as they can survive the fall
 * Depending on difficulty, they are willing to take more damage
 * Creepers
 * Will start exploding when they hit the ground, with explosions being more imminent with higher falls
 * Can now have custom explosion radius and fuse timer using edited mob spawners and NBT tags
 * Zombies
 * Will now rarely spawn with armor of all kinds, sometimes enchanted
 * Will now rarely, depending on difficulty, spawn with the ability to pick up armor, head wear, items, blocks, weapons and tools - Armor and tools & swords are equipped automatically and will be exchanged for better gear when possible        - Items that are picked up will have a 100% chance of dropping after dying - When killed, they drop what they are holding
 * All equipped gear is functional - Swords and tools do more damage on attacks, armor protects the mob
 * Rare tool drops now are damaged when it drops
 * More advanced gear is more likely to spawn with mobs when playing on harder difficulties and rarely drops when the mob is killed by players
 * When wearing helmets, they will not burn up - Instead all damage will is applied to the helmet
 * Using modified mob spawners they can have a custom drop rate of items and hold and wear all kinds of items and blocks
 * Now have a chance, depending on difficulty, to infect villagers after killing them - The villager then gets replaced with a villager zombie on death
 * On Normal difficulty, there is a 50% chance of infection and on Hard difficulty there is a 100% chance of infection
 * Infected baby villagers turn into baby villager zombies
 * Baby zombies are 50% faster, don't age, don't burn up in the sun and can wear armor
 * Right-clicking a villager zombie under the influence of a Weakness potion with a golden apple will invert their potion effect, make them wiggle slightly and eventually turn back into a villager
 * Now rarely spawn holding iron swords or iron shovels
 * When holding something in their hands, their arms move upwards when attacking
 * Added baby zombie, which is only spawnable using mods or third-party tools
 * Will now rarely drop carrots and potatoes when killed by players
 * Skeletons
 * Will now rarely spawn with armor of all kinds, sometimes enchanted
 * Will now rarely, depending on difficulty, spawn with the ability to pick up armor, head wear, items, blocks, weapons and tools - Armor and tools & swords are equipped automatically and will be exchanged for better gear when possible        - Items that are picked up will have a 100% chance of dropping after dying - When killed, they drop what they are holding
 * All equipped gear is functional - Swords and tools do more damage on attacks, armor protects the mob
 * Rare tool drops now are damaged when it drops
 * More advanced gear is more likely to spawn with mobs when playing on harder difficulties and rarely drops when the mob is killed by players
 * Rare tool drops now are damaged when it drops
 * More advanced gear is more likely to spawn with mobs when playing on harder difficulties and rarely drops when the mob is killed by players
 * When wearing helmets, they will not burn up - Instead all damage will is applied to the helmet
 * Using modified mob spawners they can have a custom drop rate of items and hold and wear all kinds of items and blocks
 * When wearing helmets, they will not burn up - Instead all damage will is applied to the helmet
 * Now sometimes, carry enchanted bows - Those items can be dropped when killed by players
 * Zombie Pigmen
 * Will now rarely, depending on difficulty, spawn with the ability to pick up armor, head wear, items, blocks, weapons and tools - Armor and tools & swords are equipped automatically and will be exchanged for better gear when possible        - Items that are picked up will have a 100% chance of dropping after dying - When killed, they drop what they are holding
 * All equipped gear is functional - Swords and tools do more damage on attacks, armor protects the mob
 * Rare tool drops now are damaged when it drops
 * More advanced gear is more likely to spawn with mobs when playing on harder difficulties and rarely drops when the mob is killed by players
 * Using modified mob spawners they can have a custom drop rate of items and hold and wear all kinds of items and blocks
 * Now rarely carry enchanted golden swords
 * Dropped Golden Swords now sometimes are damaged
 * Added baby Zombie Pigman, which is only spawnable using mods or third-party tools
 * Villagers
 * Improved villagers to make them more self-aware
 * All villagers of one village can now like and dislike specific players
 * Will like players more for trading with them
 * Will like players less for hurting them or their golems
 * When players are really disliked, iron golems of that village can become aggressive towards those players
 * After a villager dies to natural causes, excluding mobs, while a player is within 16 blocks or if a mob kills a villager, no baby villagers will be produced in the next few minutes
 * Changed and added some trades to counteract emerald farming and improve gameplay
 * Will show particle effects indicating a change of liking towards a player
 * Pigs
 * Can now accelerate to up to 5 m/s
 * Now drop their saddle when killed
 * Slimes
 * Now spawn in swamps at night
 * Sheep 
 * Sheep from spawn eggs can now spawn natural colored sheep (white, gray, brown, pink, etc.)