There is an unused enemy in the game called Giant. This mob is a huge Zombie with considerable health and deals heavy damage. They can only be hurt by being hit in the legs. Giants were added in the last version of Survival Test, but haven't been used since. They can still be spawned through hacks, however. Additionally, they can be spawned using the command "/summon Giant" in version 1.7 of the game.

Some of the Ghast's sounds were recorded from composer and sound designer C418's pet cat.

Baby zombies can occasionally be found riding chickens.

If a Spider is spawned in the Nether, there is a very rare chance that it will spawn with a Wither Skeleton riding it. This behavior normally goes unused, because Spiders don't spawn in the Nether.

The age of a tree is determined by the number of rings on its stump. With that logic in mind, every tree in Minecraft is two years old.

It's possible to place a bed in The End. However, as the developers didn't want the player to sleep in The End, beds will explode when placed. It's possible to actually defeat the Enderdragon with precise placing of beds. Upon exploding, they will injure the Enderdragon with very high damage if it is close by.

During the development of Beta 1.7, Mojang was considering adding spike blocks that would function like a piston, except with spikes instead of a flat piston head. They instead decided to add sticky pistons that could pull blocks, and make spike blocks into a static block that could simply be pushed and pulled with the sticky pistons instead. Sticky pistons were implemented, but they couldn't decide how they wanted spike blocks to look or function.

The End Stone texture is simply an inverted cobblestone texture.

There are quite a few base potions in the game's code that were left with no method to craft them in 1.9 beta pre-release 3. These potions include: Clear, Diffuse, Artless, Thin, Bungling, Suave, Smooth, Debonair, Charming, Refined, Cordial, Sparkling, Potent, Rank, Acrid, Gross, and Stinky.

While they can still be obtained using commands, they have no effect, and take the appearance of a water bottle.

The Steve skin comes from an unfinished spiritual successor to Left 4K Dead, another game by Notch.

As of Minecraft 1.7.3, naming a Sheep "jeb_" with a nametag will cause its wool to start changing colors.

One of the splash texts in Minecraft is "Consummate V's!" This is a reference to the Homestar Runner "Strong Bad Emails" episode, "Dragon", in which Strong Bad explains how to draw Trogdor. This includes drawing "consummate 'V's" for teeth.

There's a chance that the splash text on the title screen will read "12345 is a bad password". This could be a possible reference to a scene in the 1987 film Spaceballs.

The achievement "Adventuring Time" is a reference to the Cartoon Network show "Adventure Time".

If you delete the file 'splash.txt' without deleting the META-INF folder, the splash text on the title screen will say 'missingno'. This is a reference to the infamous Glitch Pokémon, MissingNo.

The texture of the Zombie Pigman has "thx xaphobia" written on it as a credit by Notch to the skin's original creator, XaPhobia.

In the TU12 world of the Xbox 360 version of the game, it's possible to find a pyramid. Inside is a tower of 4 gold blocks placed on an obsidian block. This is a reference to Rooster Teeth's series "Let's Play", where each week 7 guys play different challenges in Minecraft: Xbox 360 Edition to win a golden tower they call the "Tower of Pimps".

There are four unused paintings in the pocket edition. Information on who drew these paintings, and their purpose, is unknown.

If you name a Mob creature "Dinnerbone" or "Grumm" (using a name tag) the creature will flip upside-down. This is an Easter egg put into the game by the developers, Nathan "Dinnerbone" Adams and Erik "Grum" Broes.

Some of the paintings in the game are maps from the game Counter-Strike.