Hey guys, I got bored of WoW and took a really long break so I've been out of the game for a while. I'm back and I just found this while messing around with some other stuff.
This requires the quest "The Might of the Warchief" The Might of the Warchief - Quest - World of Warcraft
If you have this quest, any time you cross into the subzone where it takes place garrosh will spawn to aid you with the quest. He is quite powerful, but despawns as soon as you leave the subzone. If you simply walk an inch into the subzone and keep your back facing the subzone you just came from, he will spawn outside of the designated area and become bugged. He will now follow you anywhere and attack anything you do. Enjoy!
edit: I also tested this with the alliance equivalent and it works with that too.