When Gaz sees an advertisement for the new handheld gaming console, the Game Slave 2, she decides that she really needs to go to the mall in order to get one. However, when her father insists that she takes Dib to the mall as well, he forces her to wait until Mysterious Mysteries goes off, which causes them to arrive at the mall late. Gaz, in rage, tricks Dib into running off into the underground parking lot while she attempts to get a Game Slave 2; though Gaz discovers an annoying kid managed to get the last copy so she seeks to steal his copy, all the while Dib must attempt to get out of the underground parking lot, which is filled with rat-like people who just annoy him.

It’s Halloween and the entire town is getting into the Halloween spirit; much to Zim’s dismay because he considers the entire concept to be insane and he doesn’t want filthy Earth children coming to his house. Meanwhile, Ms. Bitters sends Dib to an insane asylum because he has been acting crazier than normal, in which in truth he has been getting sucked into a nightmare world that was created due to his meddling with one of his father’s inventions. After finally getting out of the nightmare world and out of the insane asylum, Dib sees Zim’s house and decides to force Zim to come with him into the Nightmare world because he believes Zim will have the capability to put an end to all the madness, but will they manage to work together despite the fact that they’re enemies and that Zim didn’t want to help him in the first place?

When Mysterious Mysteries is having trouble in ratings due to their lack of stories, they decide to take drastic measures and they finally let Dib onto the show. Dib believes this is his best chance to reveal Zim for what he is and he plays a short clip of Zim and Dib in the woods, which actually makes the anchor of the series quite pleased. However, when Zim gets on the show the next day to attempt to prove Dib wrong, they soon get into a battle of words over the real events that occurred on that day as they both attempt to persuade the host of Mysterious Mysteries to believe what they have said.

Professor Membrane has just unveiled a world changing machine that will completely remove the entire need for fuel, though if the machine were to malfunction, it could cause a giant shockwave that would destroy all life on Earth. However, Professor Membrane refuses to turn the machine on until his children are present, in which Dib is absent because he is attempting to prevent Zim from sabotaging the machine. However, things soon take a turn for the worse as Dib falls into one of Zim’s traps and the crowd in front of Professor Membrane beings to grow uneasy over the fact that they’ve waited so long, so Professor Membrane decides to send Gaz to go find Dib and put an end to his foolishness.

The skool is holding a candy drive in order to get some finances, in which the individual who sells the most chocolate bars will get a secret mystery prize. Zim becomes interested and he attempts to find a way to sell the most chocolate bars, which causes Dib to get into the contest in order to gain a defeat over Zim. Zim soon realizes, however, that he may have to take drastic measures in order to sell more candy bars than Dib.

Gir has recently been watching a movie he rented from the local mall, in which Zim just happens to be in the room when the FBI Warning is displayed on screen. Just as Zim realizes this, he gets a phone call from the mall saying they need the video back, in which Zim begins to panic because he believes that there is foul play at hand. When his computer tells him that the FBI must be an alien hunting group, he grabs the movie and makes his way to the mall, despite the fact that he doesn’t know what to expect when he arrives.

When Zim goes to Mars to attempt to find a way to destroy the Earth, figuring that whatever killed the life on Mars may work for Earth as well, he stumbles across the face on Mars, which he later discovers that is actually the controls for a spaceship, in which the entire planet of Mars was the spaceship. Dib learns of this and he attempts to go to NASAPLACE in order to get them to see what Zim is doing, but they refuse to believe him as they can’t look at the monitors. Will Dib be able to find a way to stop Zim before he uses the red planet to squish all the life out of the Earth?

When Zim is attempting to explain to the Almighty Tallest that the humans are both dumb and tall, he gets interrupted when the doorbell rings and his transmission to the Tallest is cut short. The two individuals at the door claim to be human, but Zim doesn’t believe them and he attempts to tell them that their spaceship is jamming his signal; they respond by merely sacking both Gir and Zim and taking them to their spaceship. Will Zim be able to get back to his base and finish his report to the Tallest, and what will Zim do to the two aliens who dared to capture him?

When Professor Membrane invites some of his colleagues over to the house, they insult and mock Dib because of his hobby of paranormal investigation. Matters become even worse for Dib when Mysterious Mysteries begins to show a segment on Chickenfoot, a being that is obviously a guy in a suit. Dib decides to go on a crusade to prove Chickenfoot is a fraud in order to establish the fact that paranormal investigation also disproves the frauds along with proving the real mysteries, though will Dib be able to find the elusive Chickenfoot and even if he does, how will he manage to get the suit off of him?

The Almighty tallest are examining a storage planet in order to send valuable goods to the Invaders to help them on their missions. They decide to send a Megadoomer Combat Stealth Mech to Invader Tenn to help her conquest of the planet Meekrob and they decide to send a box of malfunctioning SIR units to Invader ZIM, but when the two packages addresses are switched by an angry slave, ZIM gets the Megadoomer and plans to use his new gift from the Tallest to put an end to Dib once and for all.

When at skool one day, a child comes into class late because his head was itchy, which Ms. Bitters recognizes that it was due to lice. Before she can do anything, however, the lice infect the rest of the students in the class, so Ms, Bitters informs the Delouser, who proclaims martial law and the children are taken into separate rooms. However, Zim shows no sign of being infected by the lice, which causes the Delouser to take special interest in him.

An Irken masquerades as the new girl at school in order to settle an old score with Zim.

When Zim attempts to taint the Earth’s cow-meat supply with sewer water is ruined because of Gir’s antics, he decides to increase the power on Gir’s behavioral modifier, which will permit him to stay in serious mode all the time. However, when the serious Gir starts to consider Zim a threat to the mission and runs off to learn things on his own accord, it’s up to Zim and Squidman to find Gir and turn down the power on his behavioral modifier before too many individuals see them and jeopardize their mission.

While at school one day, Zim throws another fit about the lunch food so Dib throws a muffin at him, which causes Zim to run away in anger. The next day, a pair of Meekrob come to Dib in his sleep and grant him marvelous super powers, in which Dib decides to use to put an end to Zim once and for all. When Dib manages to suppress Zim quite easily, he decides to use his power for the greater good and he lives out the wonderful life he always wanted to have; though perhaps it’s too wonderful.

When Zim’s constant requests to the Tallest get on their nerves, they attempt to remind him that he is an Invader, not a battle soldier, and that he doesn’t have the training to use the equipment he requested. In order for Zim to prove himself to them, they send him to Hobo 13, an elite training facility that only the best of soldiers stand a chance of completing. While the Tallest hope that Zim will die on the mission and be gone once and for all, they soon discover that Zim is much more cunning than they gave him credit for.

During Probing Day, the day where the Tallest evaluate the Invaders’ performances, Zim has Dib captured in a space-time-field prison which is keeping him in slow motion, in which Zim wants to perform experiments on him for the Tallest. However, when a malfunction causes the prison to explode, Zim finds a piece of explosion that is expanding very slowly; in which Zim believes he can end if he throws it into the city’s cesspool. However, when he discovers that getting the explosion to the cesspool is much more difficult than he expected, he finds that he may just have to use unconventional means to complete the task.

Class elections find Zim running against a Dib-backed Willy for president.

Gaz develops an unhealthy fondness for the flavor of pork.

Zim's former boss is mad at him for leaving, so he kidnaps him and makes him work at his old job on the planet Foodcourtia.

When a girl named Moofy comes to Zim’s house and attempts to sell him cookies, he freaks out and sends a robot gopher to get rid of her. However, when Moofy falls into a hole, the story breaks out and a crowd of people and a news agency shows up to cover the breaking events. Zim is worried because he doesn’t want his identity to be revealed, though he begins to formulate a method to exploit the moment to free Moofy and help him destroy the world.

After Zim watches an old movie where some invading aliens are defeated by some bacteria, he begins to study germs more. However, when he discovers that such germs truthfully are everywhere, he begins a crusade to kill every germ in his headquarters so that he can be safe, which is helped by the fact that Gir had some cleaning spray handy in the house; though when the cleaning bottle runes dry, Zim must attempt to go to the store and get some more, despite the fact that he knows just how many germs are out there.

Ms. Bitters is assigning students their mentors for Career Day through the use of an aptitude test and a machine. Both Dim and Zim attempt to get their desired professions on the test, in which Dib manages to get paired with a Paranormal Investigator while Zim gets stuck working at a fast food facility. However, when Zim misinterprets the 8 billion served sign and thinks that the individuals in charge of the company are the leaders of the planet, he becomes dedicated to his job in hopes of being promoted to Lord of All Humans. However, thanks to the alignment of the planets, Zim is about to go through some uncontrollable changes that could jeopardize his mission; which Dib is looking to exploit, though both Zim and Dib find their situations to go much different than they anticipated.

Zim is upset because all of the other Invaders are doing much better in their tasks than he is, though he inadvertently discovers that his signal to the data hub has been interrupted. When Zim takes a closer look, he discovers that the Earth has actually been hijacked by the Planet-Jackers, an alien race who must throw other planets into their dying sun in order to survive. Zim begins to formulate a plan to stop the Planet-Jackers, but when Dib refuses to believe him, he realizes that he must save the world he plans to destroy by himself, just for the sake of being the one who gets to destroy it.

When Zim comes home from a lousy day at skool because he found out that Dib knows a flaw in his security system, Gir attempts to cheer him up by rubbing bacon oil all over his face. However, when Zim develops a pimple due to the grease, he fears that he will be considered abnormal and that it will jeopardize his mission. Zim believe he can use some acne medicine to get rid of the pimple, but when it only gets worse and when Gir draws a little face on the pimple, Zim believes all hope is lost; though Zim soon discovers the pimple has hypnotic powers and he hopes to exploit this new power in order to get Dib to reveal his secret.

When Dib finally manages to get a spy camera inside Zim’s house, he plans to exploit the moment to show the Swollen Eyeball Network the truth about Zim’s nature. Unfortunately for Dib, Zim is more concerned with Gir’s waffles than his next evil plan, which causes Dib some complications as there is nothing special about waffles. However, when something out of the ordinary does occur, Dib believes he may just have a chance to succeed in his plans.