Master Yo gives his young protégés a test, which involves having them watch a seemingly harmless rock named Hershel.

Carl, the Evil Cockroach wizard, gives Yin and Yang a new TV with only one remote. Yin and Yang fight over the remote, giving Carl a chance to destroy them.

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 try to teach Yo that it's not good to boss kids around, but little do they know, Herman the Evil Ant is waiting for the panda to leave so he can conquer the world.

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.