Bah, you alliance goons are all alike
You need Da' good voodoo for this one. Head to Sen Jin Village with your Troll, do the quests from there and you get acess to the Witchdoctor in training. The effects are random regardless of wether you complain of fallen arches or the gout, but one of them is a giant growth so big you're nearly eye height with the second story of the inn! I'm a MGTS fan myself so I never bothered trying the stack but I suppose you could try to stack that with the other potion effects for an even bigger one. You could go Orc I suppose but they're not as tall as Trolls... or for the biggest moo Tauren are taller than Trolls even... but I don't know how popular a mega-GTS Tauren doing the Electric Slide would be
Truth be told though the effects are so random you'll likely end up a drunken ghost watching shadow trolls dance around you before you grow. If anyone tries this I'd get a kick out of the screenshots myself. I mentioned it to Min some time back but he doesn't have any Horde toons.