Famed Mimic Gogo

Gogo is a boss in Final Fantasy V. Gogo appears and guards a crystal shard in the sunken Walse Tower in World Three. It should be noted that the easiest way to defeat Gogo is to do nothing at all: he tells them he will Mimic them, and to defeat him, they must mimic him (i.e. do nothing). Eventually, he praises the party for mimicking him, and gives them the Crystal shard for the Mime job class.

However if the player decides to attack Gogo he will be the most powerful boss in the game. He will counter physical attacks with one of his own, dealing 9,999 damage, essentially killing the target. If the player decides to use magic then he will counter with a spell that should kill the target. In addition, if the party gets Gogo down to a certain amount of HP, he will Triplecast Meteor which should kill your party unless one is at an absurdly high level or is using cheats.

Trivia

 * According to his official bestiary entry, Gogo is weak against and immune to Water. This is ironic because the entire battle against him, and all of Walse Tower where you encounter him, is underwater.
 * It is believed by some fans that Famed Mimic Gogo is actually the true identity of Gogo from Final Fantasy VI. The reasoning behind this is that besides sharing the same name and similar appearances, Famed Mimic Gogo threw himself into a time/space warp, and some fans think he was transported to the world of Final Fantasy VI.