Early in the game's history, a user posted a story on the Minecraft forums. It said that the user spawned in a new world. As the user was exploring, he encountered several structures that didn't normally spawn in the game, including, but not limited to: underwater pyramids and 1x2 tunnels. The user thought nothing of it until, in the distance, he saw a figure, resembling Steve(the default player skin) with his eyes rolled back. As soon as the user saw this entity, it ran away quickly in to the fog, but not before the user took an image of the mysterious being. It spawned many CREEPYPASTAS and stories, but Notch has stated that Herobrine does not exist. However, he can be seen in different artwork for the game, but this is likely a joke. In many patch notes, it will say, "removed Herobrine", this is because Notch wanted people to know that Herobrine isn't real.
In the PC editon of Minecraft, there is an unused mob known as the Giant. It was first added during the last stages of infdev as a new hostile mob. However, it stopped spawning naturaly during early Alpha. As of Minecraft 1.8, they can only be spawned using commands(cheats) and their AI have been removed.
Sheep have an 81.863% chance of having white wool. Light grey, dark grey, and black sheep have a 5% chance of spawning. Brown sheep have a 3% chance of spawning, and pink sheep have a 0.164% chance of spawning.
The game allows you to choose 4 different game modes: creative, in which the player can fly and have unlimited resources and survival, where the player needs to survive and obtain their own resources. Adventure, where blocks are unbreakable, unless you have certain tools. Spectator, where you can fly, but not interact with the surrounding environment, and Hardcore, which is survival locked on hardest difficulty, and death deletes your world.