Minecraft

Minecraft is a brilliant indie survival-sandbox thing.

Splash Text Error Checking
If the game detects that splashes.txt is missing (the file containing the randomly-selected yellow text that is displayed on the title screen), it will use "missingno" as the splash text instead.

Locked Chest
The Beta 1.4 update introduced "Steve Co. Supply Crates" that would be created in newly-generated chunks. It was a silly little April Fools' Day prank and a silly little Team Fortress 2 reference! The chests were removed in the 1.4_01 patch, but can still be placed using inventory hacks or with the command "/give USERNAME 95".

In snapshots 13w37a-13w39b use "/setblock ~ ~ ~ minecraft:chest_locked_aprilfools_super_old_legacy_we_should_not_even_have_this" instead. Locked chests were completely removed in snapshot 13w41a and replaced with stained glass.

At the time, the chests were indestructible. After Minecraft was updated to Beta 1.4_01, the locked chest block was able to be destroyed in one hit, and if left untouched would decay over time similarly to leaf blocks. Additionally, it generated light equivalent to a Glowstone block.

Not surprisingly, when the storage chests were updated to use smaller, animated models in Beta 1.8, the locked chests were not changed.

Their textures were reverted to the blank purple texture in snapshot 12w21a, replaced with the Block of Emerald texture in snapshot 12w22a, replaced again with the Block of Redstone texture in 13w01a, replaced once again in 13w03a with a texture that reads "missing texture", and finally to this texture that parodies the texture used in games based on the Source engine (such as Team Fortress 2) when a texture is missing.

As of 1.7, the Locked Chest has been removed and its data value used for 16 colors of stained glass.

Sky Dimension
Notch was planning to add a Sky Dimension for the Beta 1.8 update, which you had a chance of going to when you fell asleep. This feature was never implemented, but in Betas 1.6 and 1.7, there is data in the code for this dimension. With the use of mods, it is possible to access this dimension.

Sponge


The sponge block from Classic is still present in the game, although it has no use and cannot be crafted or obtained through regular means.

It can be hacked into the inventory, given to a player under SMP using "/give" or obtained semi-legitimately in the Creative mode (introduced in Beta 1.8), however it no longer works, instead behaving like a standard block. Its progamming for detecting water around it still remains in the game, however the programming for actually removing the water doesn't exist anymore.

Unused Human Mob
Before the Adventure Update, there was a partially disabled mob that was used to test damage and AI, named "Human" (Later renamed to "Monster") but was never completely removed. It ran slightly faster than the Zombie, and was slightly taller than the Player. It uses the default Player character skin, but has its own file.

deadmau5 Camera
hFY-PhJYjtg While technically used, but only under special circumstances, there is a special set of camera debugging options enabled in versions 1.9pre5 and 12w08a that were only intended for use at deadmau5 concerts. In versions after 1.9pre5 and 12w08a, these options are disabled by default, but can be enabled by using a mod to reactivate the features. In the code, these features are referred to as "debugCam".

Controls
F5 causes the camera to go into a free-look mode.
 * F9 freezes the camera in place. Pressing any two functionally connected keys (except U and O) at the same time unfreezes the camera.
 * I, J, K, and L all rotate the camera up, left, down, and right respectively.
 * U and O move the camera forwards and backwards.
 * Y and H change the field of view. Pressing these keys at the same time resets the FOV.
 * N and M change the camera's tilt. B resets the tilt.

Unused Potions
These potions all exist in-game, but cannot be brewed or obtained legitimately. All of them act like base potions in that their appearance is a bottle of water and they have no effect when drunk. They can be obtained by modifying a potion's damage value with an inventory editor, or with the /give command on servers.

Missing Potions

 * Stinky
 * Acrid
 * Harsh
 * Rank
 * Odorless
 * Foul
 * Potent
 * Sparkling
 * Cordial
 * Refined
 * Dashing
 * Charming
 * Fancy
 * Elegant
 * Gross
 * Debonair
 * Suave
 * Smooth
 * Buttered
 * Bungling
 * Bulky
 * Flat
 * Thin
 * Artless
 * Diffuse
 * Milky
 * Clear
 * Bland
 * Uninteresting

Unused Potion Effects
There are many potion effects in Minecraft, and over half of them don't correspond to any existing potion or item. Some of them don't even have their effects properly implemented! However, all of them have have the names of their corresponding potions defined in the language files. As of Minecraft 1.5, they can be obtained with the /effect command, using the appropriate effect IDs.

Mining Fatigue (ID: 4) - The opposite of the Haste effect: decreases the player's block-breaking speed, similar to what happens when trying to mine underwater. Most likely would have been brewed by corrupting a Haste potion with a fermented spider eye.

Health Boost (ID: 21) - Adds one heart to the health bar. It was later replaced by the Absorption (ID: 22) effect.

Saturation (ID: 23) - Adds one hungerpoint to the hunger bar.

Unused Text
Minecraft Multiplayer is currently not finished, but there is some buggy early testing going on.

A remnant from an early version of SMP. Not used anywhere.

%1$s was pummeled by %2$s

Supposed to be used when a player is killed by a snowball, egg, or Ender pearl, but is unused because these items do not cause any damage when thrown. It can be seen using server mods, however.

Ruby Ore

Ruby

Unused text for the Ruby and Ruby Ore.

translation.test.none=Hello, world! translation.test.complex=Prefix, %s%2$s again %s and %1$s lastly %s and also %1$s again! translation.test.escape=%%s %%%s %%%%s %%%%%s translation.test.invalid=hi % translation.test.invalid2=hi % s translation.test.args=%s %s translation.test.world=world

This might have been used to test different languages of Minecraft before languages were fully implemented.

Adventure Same as survival mode, but blocks can't be added or removed

Text that should be used for picking your game mode when creating a world, but isn't. Adventure Mode can only be accessed by using the cheat "/gamemode 2".

Seeing unused translations ingame
It is possible to see the normally unused Adventure Mode translation in-game by modifying the game code in GuiCreateWorld.java with the code below (tested in 1.6.4). This code makes the game mode selectable: else if (par1GuiButton.id == 2) {               if (this.gameMode.equals("survival")) {                   if (!this.commandsToggled) {                       this.commandsAllowed = false; }

this.isHardcore = false; this.gameMode = "hardcore"; this.isHardcore = true; this.buttonAllowCommands.enabled = false; this.buttonBonusItems.enabled = false; this.updateButtonText; }               else if (this.gameMode.equals("hardcore")) {                   if (!this.commandsToggled) {                       this.commandsAllowed = true; }

this.isHardcore = false; this.gameMode = "creative"; this.updateButtonText; this.isHardcore = false; this.buttonAllowCommands.enabled = true; this.buttonBonusItems.enabled = true; }                else {                   if (!this.commandsToggled) {                       this.commandsAllowed = false; }                   this.gameMode = "adventure"; this.updateButtonText; this.isHardcore = false; this.buttonAllowCommands.enabled = false; this.buttonBonusItems.enabled = true; }

Minceraft?
Very rarely (about one out of every 10,000 startups), the Minecraft logo is rearranged to read "Minceraft" instead of the usual "Minecraft". This is the secret that Notch said was not found yet. In crash logs at times, one may see the text "You should try our sister game, Minceraft!".

Upside-Down Mobs


As of 1.6.1, any mobs named Dinnerbone or Grumm (after two of the game's developers) will be rendered upside-down.

Rainbow Sheep
As of 1.7.3, sheep named jeb_ (after one of the main developers) will be changing it's wool color, in a rainbow fashion.