WoWDB

This Feat of Strength achievement is earned through the item  Murloc Costume, which was a reward to attendees of Blizzcon in 2007. That year's convention did not offer an online streaming service, so owners of this item either physically attended Blizzcon or purchased the code from someone who did.

The achievement is credited to any character who possesses the item at any point.  Since the costume is BoA, you can credit this Feat to all your characters by mailing the suit around.  (I am not sure why you would care since achievements are account-wide, but in the event you do)