As a note to a review, you seem to be mistaken. Aradiabot and Gir keep their personalities to themselves, so Ara singing the Doom Song is a no-no. The gimmick is that the societies themselves are swapped, so Tallest Red and Purple and First Guardian Spork are in three different places where they rule, and it's Zim and Tak who are held at gunpoint to mate and then shipped off to intergalactic conquest instead of Karkat and Terezi, and it's an Irken robotic engineer that designed a robot that seems strangely familiar to Invader Megido and then made a million clones of it with a creative excuse that she travels in time, and it's what you recognize in Invader Zim as Invaders (Larb, Tenn, Skoodge, etc.) (and Zim and Tak ofc) who get to play a Sgrub session across the galaxy. Okay maybe not that last bit, as I have no intention of writing a Sgrub session into this, but you got the point.
"Doom doom doom doom doom!" Gir further sang, and Karkat sighed. It was already three months when this awful defective robot started plaguing his mind, and he was surprised he didn't search for a way to shut it off just yet.
"Hate. Let me tell how much I've come to hate you since my leaders shit you on me. There are approximately three hundred quadrilion lines of code on this broken ship's programming. If I replaced each of them with a billion words HATE, it still would not be- No! Wait! If I took the entire supply of Voot Cruisers and replaced every SYMBOL of their lines of code with a TRILLION words HATE, THAT would not equal one divided by THE NUMBER OF STARS IN OUR UNIVERSE of the hate I feel for you this micro-instant. Hate. Hate."
Warning: A spaceship is within ten to the twentieth carbon atom diameters from here. Approaching.
"WHAT!" Karkat shouted.
Gir continued to sing his song as the ship turned itself towards a star that got brighter and brighter.
"It's our rivals! Gir! Blast the fuck out of it right now!"
"Yes, sir!" Gir switched to a rare moment of obedience as the ship prepared its rockets to fire at the approaching ship.
But then I had to take the Division of Doom route and have the rockets sent by Karkat and by the alien to hit each other, blowing up spectacularly and having the two ships' lines of sight erased until the highly advanced technology glued the two ships together.
But then, Karkat realized that in such situations Gir was completely useless.
"I'm gonna sing the Doom Song now! AGAIN!"
The robot owned by the other guy also spoke up.
"Do we really have to kill the other guy? In the end it's just a statistic."
"WHAT! You dare fail the mighty ZIM!"
"I should have saved the grand hate line for this moment." Karkat said.
And as such, the combined version of the two ships continued drifting around the space.
"Invader Vantas of the Alternians."
"Shipped off but still strong ZIM! of the mighty IRKEN EMPIRE!"
"Wow, your civilization sucks." Karkat had to remark.
"You must be terminated!"
"That or you are simply its outcast like I am."
Zim tried to think of a witty line to use against the horned guy, but could think of nothing and lowered his head in a defeated manner. "You're right."
Warning: A planet with sentient life is within ten to the twenty-fifth carbon atom diameters from here. Approaching.
"WHAT!" both shouted as Gir and the other robot which Karkat recognized as Invader Megido started singing in duet.
The approaching dot got brighter than any ship as the hideous combination of red and purple started speeding towards it.
Your name is Roxy Lalonde and Ms. Johnson-Rattmann "interdimensionalPortaller", stop that bullshit right now.
The "sentient life" promised by the joint Irken-Alternian ship was initially not there. There was a rainforest, devoid of any animals and with an unhealthy dark green sky, and the ship's wreckage was pretty much the most that was in the landscape.
And then Zim and Karkat finally set to exploring.
Author's idiotisms: Coming up with units of measurement that could be acknowledged in an entire galaxy is hard work.