The Dancing Dagger bug is a bug in the iOS version of Final Fantasy V which can be considered as a benefit for the player. This bug involves the Dancing Dagger and a character with an ability to wield two weapons, one in each hand (Ninja for the example).
In the previous version of the game, if the Dancing Dagger is equipped with another weapon in the other hand, the dancing effect of the dagger will not allow the other weapon to attack (except for the "Sword Dance" which allow the character to attack with both weapons) but in the iOS version, the other weapon can be used to attack after the dancing abilities, this bug making "Sword Dance" to attack three times (1 time with the Dancing Dagger and 2 times with the other weapon). This bug also occurs with the Thief Knife when the weapon tries to steal.
If the Dancing Dagger uses "Jitterbug" that kills the enemy, the attack from the other weapon will bring the vanished enemy back on the screen. The enemy counts as defeated, and will never attack. The battle is won after killing all other enemies.