Spawn Egg

A Spawner Egg is a new item added in the weekly pre-release 11w49a. It can only be legally obtained in creative mode. There are several different types of spawner egg, each type spawning a different mob. A mob is spawned by right-clicking on an empty space while holding the egg.

There is a spawner egg for certain mobs only;

Trivia

 * There are good explanations for why the unspawnable mobs cannot be spawned. A Snow Golem can be easily created, a Spider Jockey is not a separate mob as such, Enderdragons are not supposed to be spawned other than the one in The End(and could easily be used to grief if spawned in other dimensions), and Giants are completely unused.