Okay this is HORDE only, which is a shame but I can see why, it means though however as long as you don't die you will forever look like a goblin :')
Azuregos - NPC - World of Warcraft
Complete this quest and you shall get
Faded Wizard Hat - Item - World of Warcraft
Equip it , right click it and the buff to make you look like a goblin lasts 30 minutes with a 30 minute cool down. Pretty straight forward.
However once you have the buff you can put your normal helm back on... Thanks
The quest line