This is obtained via Being a Champion of Ironforge in The Argent Tournament.It takes 40 Champion's Seals.In order to get the seals you have to do dailies in the tent with the chick who gives the black knight quest.Here are some of the other Alliance pets
http://thottbot.com/i44984 Dranei Pet(Little Flower that moves)
http://thottbot.com/i44974 Human Pet (A lamb)
http://thottbot.com/i45002 Gnome Pet (A mini version of there mount)
http://thottbot.com/i44965 Night Elf Pet(A treant)
In order to get each of those pets,you have to become a champion with their and pay up 40 Champion Seals. Note that it is possible to get The Opposite Factions Pets From The Neutraul Auction House,which is awsome for getting The Sen'jin Fetish http://thottbot.com/i45606. All pets are BoU(Bind on Use).
Hopefully this has been helpful. Please Vote this up whoever reads it.