Kul Tiran Up the Dance Floor

Requires 2 players. Both playes need to target one another and type /dance (can make a macro)
Can dance with players of hostile faction.

The dance floor is in the north part of the Norwington Estate in Tiragarde Sound.
/way Tiragarde Sound 50.53 24.33 Norwington Estate dance floor

Demo video: https://www.youtube.com/watch?v=M9oJH3mBE6A

Ps: For alliance it is easy, but for the horde you can have problems with guards.
Closest Horde windriders: Wolf's Den -Tiragarde Sound or Mudfisher Cove - Drustvar
If you still need to unloock them, try to go from main horde hub near the Bridgeport to the west and then swim north to the other side.

Soloable!

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• Have two Alliance toons with same state of WM, get portal to Boralus and move them both to the dancing pad: 50.30 25.15 in Tiragarde Sound.
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• Start /dance on one of them and alt-f4 the game.
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• Log in onto the second toon quickly and /dance with your alt-f4-ed toon. You have like <60 seconds until the alt-f4-ed toon will be actually logged off and vanish.
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Keep in mind the toons happened to land on same shard. If not, you can create group in lfg and join the toon into a group with additional alt-f4 trickery. I happened to have toons both 60 lvl so propably it helped to put them in same shard.

Make sure you get the right dance floor! There are two. One right by the mansion on the hill and one in the grounds. You want the one in the grounds. You can access it from the river that flows past it on the northern side of the estate.
I found that part out the hard way. ^^
The achievment is instantanious as soon as the other player also /dance with you. This is good as you will be attacked by guards immediately when you go near the dance floor as horde.