Another Code name for "The Boss" in the popular video game "Metal Gear Solid 3". "The Joy" is the Cobra Unit name for the boss and she is rarely refered to as it. She trained Naked Snake from an early age and, also, the other members of the Cobra Unit. After being defeated by Naked Snake in battle, the Joy says that there can only be one Boss in the world and, afterwards, Snake is refered to as Big Boss, seeing as he has surpased even the Boss. Even after that, The Boss is still the Joy.
If the Boss had a bomb in her like the other Cobras, she would shout out "The Joy!" and then explode.