Yin and Yang tell Yo that he is old, and Yo makes them pick up his medication. Yo throws a party to look cool, but Yin and Yang make Yo's old enemy, Kraggler, mad. Kraggler turns everyone, except Yin and Yang, into old people.

Yin and Yang wish to lose their bossiness and aggression and in the process accidentally create a new villain, Yuck.

Yang fakes being a Woo Foo Warrior to impress a girl. To prove his skills, he has to take out a huge steel beetle.

Yin and Yang get into a fight while cleaning their room, and when Yin costs Yang the world record at a video game, he refuses to shower until one of them cracks and apologizes. But Yang is soon encouraged to clean himself up when his odor attracts the amorous advances of Malodia the Elephant, Princess of the Stink Aardvarks.

Yin comes down with a case of the Woo Foo Flu, an illness that causes her to bend reality whenever she sneezes. Master Yo orders Yang to take care of her while Master Yo concocts an antidote for the Woo Foo Flu. However, Yin later gets captured by Carl - who intends to exploit her illness so it can help him take over the world - and Yang may have to get himself sick to save Yin.

Yin and Yang use Zarnot to boost their popularity by lying. When Zarnot becomes huge, they must prove that they are telling the truth.

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Yin's Woo Foo Aura gets out of control, trying to save the environment and escapes Yin's body, destroying the town.

Yin falls in love with a person named Brett who actually turns out to be Yuck.

Yin and Yang have to stop Pondscum from stealing Yo's golden chair.

Kraggler uses the cronalogicum to trade ages with Yin and Yang so he can become young again.

Yang won a doll at the county fair for Yin, but the doll is actually Zarnot.

Yo tells Yin to go to the valley of the two-ni-corns and find a rainbow mane The Gnu to fix her toy. Meanwhile, Yang is taken over by Ultimoose.

Saranoia makes a snow day so that Yin and Yang can play outside and Yin may have a day off, as she holds an obsession with Yin's future

The Night Master rebuilds his armies that were frozen years ago by Master Yo. Little do they know, Yin and Yang are involved in his plan.

Yang is thrilled that the CPK (Chung Pow Kitties; a pastiche of Hello Kitty and Powerpuff Girls), a rock band made of cats with mad ninja skills in town. Not only that, but they also appear on Broadway and are looking for a new member. Having a sharp sword is a requirement. Yang's bamboo sword isn't sharp enough, but Master Yo refuses to give Yang a new sword. Yang plots to steal weapons from the Forbidden Armory to try to make the cut.

Yin meets a hamster who loves to clean while she is out buying cleaning supplies. The hamster reveals himself to be Fastidious, and asks the Woo Foo students to help him defeat some of the spirits who have been making a mess. However, there is something sinister about Fastidious.

Yin and Yang are fishing when a group of female pirates appear. They act really nice towards Yin, but not so much towards Yang. Are these pirates all they appear to be, or is there something else about them?

Carl wants to use his mother's destructive jewelry for his nefarious purposes (especially since she never wears them) but his mother, Edna, won't let him. Meanwhile, Yang pulls a practical joke on Master Yo by posting his bio on a website for dating service for old people. Master Yo's blind date turns out to be Edna. Can Yin and Yang break up this relationship that's not meant to be before Carl can take advantage of his mother's absence?

Master Yo shows Yin and Yang that black-and-white films can be scary.

Yin uses the misfortune cookies on Yang to take away his good luck.

Yang is really interested in a girl named Lina, who is Yin's really good friend. The trouble is, Yang's behavior turns Lina off. So Master Yo suggests that Yang should try to be more like Yin in order to make Lina like him.

Yin and Yang are fed up with not getting an allowance from Master Yo for doing chores around the dojo. Then a stranger appears, announcing the opening of a new UltraMega Mall in their town and giving the two young warriors credit cards to their heart's content. Are Yin and Yang playing directly into an evil villain's plans?

Yin and Yang host an awards show for evil Brother Herman.

The Night Master hides in Yang's imagination.

A new master is in charge.

A fun road trip serves as a cover for a covert operation.

Dressed as a donkey, Yin and Yang infiltrate a bad-guy convention.

Saranoia returns.

Yin and Yang meet the legendary Woo Foo twins.

Coop teams up with Yin and Yang to win back an ancient Woo Foo artifact.

Herman and Carl want to give their mom a pair of rabbit's feet for luck.

Master Yo's ex-girlfriends show up.

Yang finally makes some guy friends, but they're not who they say they are.

Brother Herman attacks while Master Yo is away.

A heavy-handed hero teaches everyone a lesson.

Yin and Yang wonder if Master Yo is really evil.

Yang acts up in a video game.

Yin and Yang are put on trial.

Yin and Yang follow Yuck to a terrifying place... inside Master Yo.

Shaggler turns into a baby.

Yang uses an ancient tool to end Yin's constant pursuit of popularity.

Yin and Yang are promoted.

Information on Yin and Yang is leaked to the Night Master and the twins try to find the culprit.

The Night Master plots to kidnap Master Yo so he can plunge the world into darkness and be free.