Zorc Arm Dragon
Yu-Gi-Oh! Duel 54: "Millennium Enemy 5: Stop the Run of Criticals!"
Yu-Gi-Oh! (first series) Episode 26: "Rival Clash - The Greatest Crisis"
After Hiroto shot off Zorc's left arm, it turned into 2 monsters, Zorc Arm Dragon and an eyeball. After Joey took out the eyeball, Yugi tried to brainwash Zorc Arm Dragon. There was only a 10% chance of it working, but using his "double hit" strategy with the dice, Dark Yugi was able to roll a critical allowing Yugi to brainwash the dragon.
Now known as Pao, the dragon joined Yugi's party and helped them fight Zorc, when they got to the castle.