Spawn Egg

A spawn egg is an item used to spawn mobs directly.

Obtaining
Spawn eggs can only be obtained in Creative mode, or by commands. In Creative mode, the player can press on an existing mob to obtain their respective egg. Spawn eggs are also available in the Creative inventory. There are 43 eggs available in all editions (45 in Java Edition 1.13).

Commands
Spawn eggs can be obtained by ops using. See here for all available spawn eggs and commands.

Any spawn eggs not listed in the table below cannot spawn entities. They will instead make a sound as though an arrow has been shot. These eggs will be the default color, white with gray spots. When a player hovers over the image with their mouse the name of the egg is "Spawn ". This egg has no specific properties and can not spawn any mob, except for Bedrock Edition in which some "hidden" spawn eggs obtained from commands that spawn other entities like primed TNT and wither skulls.

Usage
A spawn egg is used by pressing on any surface (top, bottom or side) with the egg. When used on a top surface, the egg's mob will appear with its feet immediately adjacent to the surface. The egg will be consumed in the process in Survival mode, but will not be consumed in Creative mode.

Spawn eggs are not thrown (unlike normal eggs); the player must be within normal range of the block to use the spawn egg. Hostile and neutral mobs (except wolves and polar bears) spawned while on Peaceful difficulty will be created but then instantly deleted from the world.

Dispensers
A spawn egg fired from a dispenser will spawn the mob directly in front of the dispenser.

If on a adult passive mob
If a spawn egg for a passive mob that has a baby form is on an existing one of that same mob, it will spawn a new baby version of that mob, rather than an adult.

Monster spawners
Any spawn egg can also be on a monster spawner to change the mob the spawner spawns.

Renaming
Spawn eggs can be renamed on an anvil, and when used will spawn mobs with that name appearing over their head. Their names can only be seen if they are aimed at from four or fewer blocks away. This name will also appear in death messages from the mob killing a player. If you rename a spawn egg by the names described below, the mob will appear described below.

Java Edition
The data value of a spawn egg has no effect; instead, the  data tag is being used. For example, would cause the spawn egg to create creepers.

If, for the entity tag 'id', a SaveGame ID is used for a mob or other entity that is not listed in the table above, such as  (iron golem), the result would be a spawn egg with the expected name ("Spawn Iron Golem"), but will be the default color (white with grey spots). These eggs cannot be used to spawn mobs directly, but can be used to program a mob spawner.

Bedrock Edition
When using the command to give a spawn egg, it requires the numeric ID of an entity; for example:  would give an egg that spawns a creeper. For reference, see Bedrock Edition data values for a complete list of entity IDs.

Eggs can be given not just for mobs listed in the table above, but for a few other entities. These eggs will be uncolored (white with grey spots), and will be called by unlocalized placeholder names, or simply, "Spawn".
 * The snow golem (21), iron golem (20) and item (64) spawn eggs can be given, but will spawn nothing.
 * The ender crystal spawn egg (71) produces an end crystal.
 * The boat (90) egg will place a boat on the ground.
 * Using any other entity ID will fail to give the egg.

Trivia

 * Data values differ between platforms. However, the ID is the same.
 * "Player" spawn eggs can be generated, but are useless. This is because they can not be spawned, even with the summon command.