Yin and Yang prepare to go on vacation. Coop returns and tried to warn them of The Night Master's energy escaping, but they ignore him until it's too late.

Coop's mom is throwing a "welcome back/thanks for saving the world all by yourself" party, and Yin and Yang are the only ones not invited. Meanwhile, three flunkies join together and try to get into The Night Master's fortress. However, they need the spare key, which the Night Master gave to Coop!

Yin and Yang are pitted against each other in a fight.

Yin takes credit for saving the mayor, without acknowledging Yang's help.

Yang's brain becomes controlled by a villain known as Mastermind.

Master Yo faces an old nemesis he has never been able to defeat.

Yin and Yang uses a magical bracelet to make fooplicates of themselves until Yuck returns.

Melodia the Aardvark Princess returns to claim Yang until Fastidous makes Yin mad with the Stink Aardvarks.

Carl casts an ugly spell on Yin and Yang after Yin insults Carl and calls him a "buglie".

Yin and Yang learn self-control at an institute, but its founder, Ultimoose, may have more sinister plans in store.

Yin and Yang get a lesson in cultural enrichment when a foreign exchange student from Redneckistan named Jobeaux shows up. Meanwhile, the Chung Pow Kitties return in search of a powerful Woo Foo artifact. Yin and Yang suspect that there is more to Jobeaux than meets the eye.

Master Yo is sick of Yin and Yang disrespecting him. Yin and Yang are sick of Master Yo treating them like babies. When young Kraggler switches ages with Yo (part of a diabolical plan), Yin and Yang are forced to babysit the three-year-old Yo, and he reveals how powerful (and bratty) he was as a child.

Yin and Yang attempt to defeat a half-human, half-bull monster.

Carl forms a league of evil with three other villains when they all rent an apartment together.

Yang endorses a toy line for money but doesn't realize that the toys are harmful to children.

Yin, Yang and some of their friends accept a free vacation to a mysterious island, not knowing that it's a trap set by Smoke.

Ultimoose and Yang search for an amulet that will give them all of the Night Master's powers.

Yin reluctantly goes on a date with Coop, and she falls under his evil spell.

Carl tricks Yin into eating seeds that make her doubt everything.

Mr. Pondscum realizes he isn't a goldfish but a polliwog.

Carl magically switches brains with Master Yo in an attempt to destroy the Woo Fo warriors.

Yin takes in some seemingly harmless green creatures as pets, but Yang believes they are dangerous.

Yin and Yang become addicted to a TV show about a superhero but learn they should focus instead on becoming heroes in real life.

Yang loses his emotions after he is zapped by Fred.

When Yang separates himself from Yin and Master Yo, he saves a robot, and they start to act like brothers. But Yin is feeling suspicious and jealous and discovers the robot is actually a spy made by Zarnot sent to destroy Yang.