Type Chat:/spawnmod enderdragon Simple, but it may not work if you don;t have certain plug-ins for servers
do /summon EnderDragon
An Ender Dragon resides in the new End dimension, which can be accessed by completing a portal in a stronghold with 10-12 Eyes of Ender. Alternatively, client mods in single player or server mods in multiplayer can be used to spawn one.
There's no spawn egg for enderdragon.
Yes, in the Nether Zombie Pigmen spawn on the netherrack but I don't think they spawn on Netherrack in the Overworld.
The eggs do not hatch, they are there for no particular purpose but can be collected and brought back to the overworld for use as decoration but will never hatch. To bring it back you need to activate a piston to move it or place a torch under it. It cannot spawn another enderdragon but it can be used as a trophy or decor.
Chickens, cows, sheep, wolves, and pigs will spawn on well lit grass in the Overworld. (Not the nether or the end.) Mooshrooms will spawn on Mycelium in the Overworld, Skeletons, creepers, spiders, bats, and zombies spawn in dark places. (Only in the Overworld.) Zombie pigmen and ghasts spawn randomly in the nether. Skeletons, and wither skeletons spawn in nether fortresses, and blazes spawn only near blaze spawners. (Found in nether fortresses.) Ocelots spawn in jungles, and squids spawn underwater in the Overworld. Endermen spawn rarely in dark places in the Overworld, or witha much higher frequency in the end. Cave spiders spawn from spawners found in abondoned mineshafts. Villagers spawn when the map is created and when other villagers breed and have babies. Slimes spawn at low elevations in slime chunks or in swamps. Silverfish spawn from their spawners in one of the worlds three(or less) strongholds. Witches spawn in witch huts when the map is created. One ender dragon spawns in the end when the map is generated. Those are all the mobs which are created naturally, for more information, I advise you go tohttp://www.minecraftwiki.net/wiki/MobsIf all these conditions are fulfilled, and no mobs are spawning, I suggest you press Esc and change your difficulty to easy, medium, or hard, as no monsters spawn while you are in peaceful mode.In creative mode you can also use Spawner Eggs (found in your inventory) to spawn mobs
You can't, it is not possible to spawn as one without the use of mods for the game.
There is no human spawn egg unless you have mods for it
The only way to spawn herobrine in minecraft is to use mods as you cannot spawn him in vanilla minecraft.
If your on PC their are a couple mods out that can let you spawn him in the game. If your playing on Console this is not possible. Its up for you to find him. ;)
There are a few mods that can do so, But they can not be spawned in vanilla minecraft.