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, and Enderdragons are not supposed to be spawned other than one final boss in The End.
 * The Enderdragon Egg may be used in a similar capacity later on.