Zin and Zang are characters from the Aladdin episode; "Opposites Detract". Zin is the good and kind-hearted one while Zang is his evil half twin. When both twins merge together, they become a powerful dragon of different colors and personalities depending on the balance between Good and Evil. If Zin were more powerful than Zang, then, they would turn together into a white dragon known as the Good Dragon, which is considered to be the city of Pei Ling's protector but if Zang were stronger, they would turn together into a red dragon known as the Evil Dragon, which prefers to destroy the city rather than protect it.
Role in the episode
At a canyon, a Chinese man named Zin Lao gets surrounded by snarling wolves. Aladdin and the others rescue him. After getting rid of the wolves, Zin tells Aladdin that there is a dragon and runs, with Aladdin confused. When Zin runs into Genie, he passes out. Aladdin and the others are riding camels in a desert taking Zin back to his home: Pei Ling.
Zin wakes up and sees that he's at his home and says that he must get away because Pei Ling is the city of the dragon. A woman shows up and tells everyone that the dragon is gone and the people are celebrating its disappearance. A parade comes towards them with two men holding a paper dragon. Aladdin and his friends see the paper dragon and tell Zin that he has nothing to worry about, but Zin runs away, telling them that they don't understand. He hides in an alley and runs into a man who looks similar to him: Zang.
Zang grabs Zin's arm and they are surrounded by a magic glow. When Aladdin is looking for Zin, everyone sees a red dragon fly towards them. Aladdin realizes that Zin was right about Pei Ling all along and tries to stop the dragon, but fails. Genie traps the dragon in a crate. The mayor of Pei Ling comes to the gang and tells them that the dragon used to be the protector of their city, but now it has become a force of chaos. For Aladdin and the others capturing the dragon, the mayor rewards them by showing them a cartload of silk cloth. When Genie picks up the crate, he notices that it's light. He looks inside and sees that the dragon is gone.
That night, the gang goes to a government warehouse to search for the dragon. They then run into Zin, who was hiding behind one of the barrels. Zin tells them that he's hiding from his evil twin Zang and says that the dragon will not attack as long as he's with them.
Aladdin suggests that they split into groups of three to find the dragon: he, Abu, and Zin will go on the south side while Genie, Iago, and Carpet go on the north. Genie, Iago, and Carpet go to a building on the north side of Pei Ling, but can't find the dragon. They then run into Zang, who they mistake for Zin. Genie tells him that he's supposed to be at the south side with Aladdin and Abu. Meanwhile at the south side, Aladdin climbs a stack of crates while Zin watches him. Zin then runs into Zang and they run. They climb up a tree and the branch Zin is on breaks and Zang catches him. The twins then get surrounded by swirling light in the shape of a yin-yang and the dragon appears.
The gang sees the dragon and fly away from it, with it chasing them. Aladdin suggests that they "take the dragon for a ride" and the dragon chases them around the city, destroying buildings. When they get to a low bridge, the dragon gets stuck. When Genie builds a brick prison around the dragon, a red light is shining out of it and Zin climbs out of the roof. The gang sees Zang and realize what's going on. Zin tells them that when he's together with Zang, they become the dragon. He also tells them that his twin has become so much stronger than him.
Zang starts to attack Zin again and the two begin to wrestle, with Iago telling them to turn into the dragon again. When Zin shouts at Iago, telling him to be quiet, Aladdin tells him to do the same for Zang. Zin pushes Zang off the roof and Carpet catches him. When he gets back, he starts to attack Aladdin. When Zin tells him to leave him alone, Zang tries attacking him. While they are fighting, they get surrounded by a glowing white light, showing that Zin is getting stronger and he is now controlling Zang. The men then fall off the roof and then turn into a white dragon. It flies over the destroyed buildings, which get rebuilt.
Zin and Zang turning into the Evil Dragon
The Evil Dragon
Zin and Zang turning into the Good Dragon (and Zang's somewhat defeat)
Their names rhyme with the words Yin and Yang, which are concepts used to describe how apparently opposite or contrary forces are actually complementary, interconnected, and interdependent in the natural world, and how they give rise to each other as they interrelate to one another.
However, in Chinese philosophy Yin represents the cold and darkness while Yang represents heat and light. Neither are truly evil, but imbalance between the two is when true evil occurs. Zin and Zang are the opposite of what they should be: Zin (named after Yin) is peaceful and friendly, and wears white clothes, while Zang (named after Yang) is cruel and cold, and wears black clothes (the evil dragon form, however, is red, which is a Yang color).