During a battle between Team Save Earth and the two Irken factions, all three groups are accidentally sent into a Mirror Universe. Now they have to deal with their counterparts in order to get back home.
- All for Nothing: The events of this chapter occur because both Dib and Tak's teams are trying to stop Zim from harvesting cosmic energy… but at the end, it turns out that GIR nabbed a crystal shard containing some of it during the big fight in the Mirror Universe, so after all that Zim still succeeded.
- Big Eater: Anti-Ying is constantly eating, and quite messily for that matter.
- Brick Joke: Upon meeting Gaz's sickeningly sweet Mirror Universe counterpart, Viera remarks that she should take a picture before they return to their own universe, which she does so at the end of the chapter.
- Enemy Mine: The three teams call a truce after being accidentally transported to the Mirror Universe. Later, they outright team up to defeat Dib and the twins' evil counterparts, who are planning to destroy both universes and Start My Own.
- Expendable Clone: Anti-Nyx has numerous clones of herself as backups in case anything happens to her. As they all have the same personality of "interchangeable corporate drones", the prime universe Nyx has a Freak Out.
- Freak Out: Nyx has one when her frustrations with her counterpart reaches a peak.
- A God Am I: Anti-Dib and Anti-Viera intend to collapse both universes and channel the leftover cosmic energies to make themselves gods of the new reality that emerges afterwards.
- Kill It with Fire: Nyx's initial reaction to meeting her counterpart, a bland corporate drone. She does eventually vaporize her, only for it to turn out she has backup clones.
- Let Us Never Speak of This Again: After returning to their own universe, Dib and Viera both make it clear to Steve that they never want to discuss how their counterparts were a couple.
- Mirror Universe: The entire plot of this chapter. Among other things, Doomsville is called Hopesville, Zim and Tak are heroic agents of the Irken Federation trying to peacefully uplift humanity, Dib and the twins are supervillains trying to Take Over the World, Professor Membrane is a hillbilly farmer, and Gaz is an extremely nice girly-girl.
- Mythology Gag: Tenn notes that the interdimensional Smarkle Rift is a smaller version of a Florpus Hole.
- Negative Space Wedgie: An explosion of compressed cosmic energy tears open a hole in reality called a Smarkle Rift, which acts as a one-way portal between universes.
- Other Me Annoys Me: No one is impressed with their Mirror Universe counterparts.
- Reverse the Polarity: The Trope Namer is referenced by means of Anti-Zim's contribution to getting everyone back to their own universe, which is a "neutron flow polarity reverser".
- She Is Not My Girlfriend: Both Dib and Viera react this way when their counterparts, who are a couple, ask if they are too.
- Ship Tease: Dib and Viera's flustered reactions to learning their counterparts are a couple.
- Shout-Out: Ying uses "I'd like to test that theory" as a Pre-Asskicking One-Liner while going up against Anti-Steve.
- Shut Up, Hannibal!: When his counterpart starts giving an Above Good and Evil speech, Dib cuts him off, saying that it makes him sound like a douche.
- Too Much Information: Ying's reaction to Nyx commenting that she's had dreams involving multiple Zims.
- Waking Non Sequitur: Zim kicks Skoodge awake after everyone is accidentally transported to the Mirror Universe, causing him to blurt out "Goat cheese omelettes!"
- When the Planets Align: The chapter's plot is kicked off by the Stellar Shower, a cosmic energy storm that passes by Earth every 857.3 years. When Viera comments on the oddly specific number, Steve counters that while magical events seem to always round to the nearest hundred years, scientific ones bound by physics aren't quite so even.
