Troll and Gnome Takeover!, or "Ohmygoodness, It's About Time"

Horde:

• Go to Orgrimmar.  Travel south out of the city to the very southern tip of Durotar.  The quest giver is on the eastern side of Sen'jin Village.

Alliance:

• Go to Ironforge and head to Tinkertown.  Talk to Mekkatorque for the quest.

Past the break are the specific questline walkthroughs.  Don't continue if you don't want spoilers.

Horde:

• Da Perfect Spies:  Loot 5 frogs.  They're everywhere outside the village.  Go back to the quest giver and right-click each frog to attune it.
• Frogs Away!:  Head to the circle of dancers just to the west of you.  There's a bat on their far side.  Talk to Handler Marnlek beside it and hit white flares with frogs (target area like an aoe) as you fly over Echo Isles.  Plenty of chances, so don't fret if you miss a few.
• Trollin' for Volunteers: Head back to the bat handler and go to Razor Hill.  You click them, use the drums, and get (I am not even joking) a posse.  I want to keep my posse.  *frownyface*  You run them back to the guy, they mount when you mount.
• Lady of Da Tigers: You're a kitty!  (A male kitty.  *pout*)  Run south to Echo Isles.  Stack 3 of your second ability, use your 3rd when it's up, use your 1st the rest of the time.
• Dance of De Spirits: Talk to the Witch Doctor.  If someone else is doing the quest, you can't speak to him until his bit is over for them.  The reward is an item that turns you into a troll (of your own gender) in full battle gear. 4 hour cooldown.  :D
• Preparin' for Battle: Talk to the bat handler.  Talk to Vol'jin on the little island.
• Zalazane's Fall: You have to wait for the battle just like when you were in the Battle for Undercity, so others will likely be there with you.  The reward is a nice RP Darkspear Cape. Tip: You don't need to be in a raid group to get the quest complete, but it's a good idea to put a raid marker on Zol'jin's head, as he can be hard to spot in a crowd.

Alliance:

• A Few Good Gnomes: Use the motivator on gnome citizens standing around.  Run your awesome posse out to Steelgrill's Depot (go south out of Ironforge and take the eastern fork in the road).  Deliver them to the guy among the crab-lookin' machines.
• Basic Orders: Head to the large group of gnomes you passed on entering the Depot.  Wait for the instructor to tell you to emote salute/roar/cheer/dance.  Have him targeted and emote when he tells you to.
• In and Out: Enter the machine, hit ejection.
• One Step Forward: Enter the machine, hit the movement buttons 3 times each.
• Press Fire: Behind the quest giver is another machine with targets.  Hop in, get in range of the targets, and fire 3 times.
• Vent Horizon: Go on the flight, target 3 of the huge marked vents with your Radiawhatsit.
• Prepping the Speech: First target is one of the mount vendors right there in the Depot.  Next, run toward Kharanos (south at the crossroads) and while on the road just north of Kharanos you'll see a little building with a turning gear on top.  Inside is your second guy.  In Kharanos, south of the inn, you'll see a small camp with wagons and behind it another small camp with a cauldron.  The cauldron camp has your last guy.
• Words for Delivery: Deliver to the crab-lookin' machines guy.
• Words for Delivery: Ride the machine, deliver the speech.  If Mekkatorque is not right beside you when you land, see if Operation Gnomeregan is in progress.  Once it ends, he'll respawn instantly.
• Operation Gnomeregan [75]: Follow Mekkatorque, stay with him, don't run ahead.  It will bug if you get ahead of him too far.

Awesome Posses