Make sure you read this. Name it JakeTheDog then tame it!
Note: Minify the command to avoid issues :)
Best command ever!
Summon JakeTheDog!
Normal pokeball
Troll your friends with this command!
Pet ENDER DRAGON!!!!!
Wither Storm Boss in ONE COMMAND
HEROBRINE COMMAND
HEROBRINE BOSS BATTLE (See YouTube for details)