While doing random things in Draenor, I found out an interesting elite named Amethon; he has an ability called "Crystalline Cage", stunning the player and morphing him (under some big purple crystal). If an another player copies the stunned guy's appearance, he will become invisible!.. So, you just have to go with a friend and the Ai-Li's Skymirror.
Well, I think you will probably get banned if you use that morph in PvP. Though, if you're more of a roleplayer it allows some interesting stuff, such as roleplaying a mount, an animated object, or even just not being visible.. (Who doesn't want to be a flying hat ?)
Now, do whatever you want with this information.