Movie Summary
G'nathus is an elite spawn that hits like a truck - altho he is worth it!
Drops one of those awesome combat pets !
http://www.wowhead.com/item=94595
Have in mind - Only NPC named "G'nathus" drops the pet - all others that look similar but are called "Spawn of" don't drop the pet.
Also in video there is a mention of this mob being soloed.
It is true - description below!
http://www.mmo-champion.com/threads/1272862-Kiting-G-nathus