Ok, In Underworld of Warcraft, in the 3.0.9. PTR realm...
Step 1: Make a Druid (doesn't matter what race or faction)
Step 2: Go to a instance (again, doesn't matter which one)
Step 3: Transform into something, I prefer Cat, not Cheetah.
Step 4: Enter the instance!
Step 5: ???
Step 6: Use all spells!
Ok so, the use of this bug is, that if u enter a instance (the portal) in a form like cat, U can use all spells from Druid spell book, such as Mark of the wild, Thorns, u can heal, and use cat skills, too! the only thing that changes is that u don't got the buff that ur transformed into a cat :/.
This is the easiest thing to do...
In simpler words: Create Druid, Go to Instance, Transform in Cat, and enter the portal of the instance, use all spells.