Transforms you into a wasp. You can fly, cast spells, and attack in this form. Only works while in Dalaran. If the elixir is used to become a wasp outside of the underbelly, for example The Eventide, you will not get the "no fly zone" debuff so long as to don't fly.
Transforms you into a hungry Tuskarr, adding +50 to your fishing skill. (This bonus stacks with fishing lures.) Interesting to note, if your character is female, this will also temporarily change your gender, including gender specific titles. For the duration of the buff you will lose Matron and gain Patron.
Causes everyone (including NPCs and players, with the exception of Zidormi at the Violet Citadel) to appear to you as human mages wearing full Netherwind Regalia. Several NPCs in the city are given random genders.
Prior to Patch 3.0.8 the object was misnamed Underbelly Elixer, this was either hotfixed or fixed in the patch.