A WoW April Fool’s Day joke some time ago purported that Blizzard was adding Two Headed Giants as a playable race, where two different players played each head. Apparently, the guys at Carpe Diem saw that as a challenge.

gamebunny:
The “Possession System”, whereby two players combine into one fighting unit sounds exciting and original. Describe how this actually works in-game.

Jon Latham:
The possession system is unique to Carpe Diem and allows two characters, the human and the fey, to work together as one. The human manoeuvres the characters around the game whilst the fey works her magic and casts the spells at the enemy. A bit like flying a world war II bomber where you have a pilot and a tail gunner doing the firing (if you get the analogy!)

My friends and I joked once about wanting to do Voltron the MMO. While a lion robot, you could fight as normal, but once your lion merged with the other robots and you were the leg of Voltron, your gameplay experience revolves around doing leggy things. Like walking. Unison with the other leg is key.

For some reason, this idea didn’t go anywhere.