Minecraft wiki entry for Things_to_do_when_bored, associated text: The command /summon can be used to spawn unique and interesting mob types. Examples of what a player could create with the command may be an upside-down spider jockey on top of a skeleton or an enderman with bedrock in its hand and a minecart on its head. Other useful commands used to place or modify blocks automatically are /setblock and /fill. The player could use these to create a giant wall or building without having to manually place everything.