Character and mount turn green when summoning Disgusting Oozeling.
I usually don’t mention companions, I think there are great sites for that. That being said, since this one triggers an effect on characters, I had to list it.
Now, this one is not so easy to farm but here are some tips found in Wowhead here: http://www.wowhead.com/npc=8607/rotting-sludge#comments
This companion can be found in a bag with a 1.5% drop chance only. The bag itself is difficult to get, drops from several mobs (1 to 10% depending on the mob.)
At the starting area for DK, a player found a spot full of these mobs with 10 to 11% drop chance for the bag.
They despawn if you complete a certain quest so be sure to read the comments in Wowhead.
So you need to create a DK and start some quests then go directly to the spot and farm them.Took me roughly 2hrs to get the pet but it’s a good spot I think.
Whatever you decide good luck, also don’t hesitate to leave a comment below!