Calvin, Hobbes, Socrates and the MTM are planning a water balloon attack on Susie one day when Socrates' transmitter chip receives a transmission from Galaxoid and Nebular, who want information about Earth to give to their leader. Calvin and Hobbes tell them what they need, and they sign off, but something goes wrong with Socrates' chip, and he picks up another transmission. All they can hear is the faint voice of someone, and what little they can make out is that someone wants to escape from somewhere and doesn't want to die, before Socrates starts screaming and writhing in pain. The MTM deactivates the chip, and Socrates remains clueless to it, but Calvin is concerned, so he takes him along to Sherman's lab to investigate.
Galaxoid and Nebular have returned to their home planet and report to King Stor, their leader. Their planet, Annkor, is dedicated to learning about other planets, and they incorporate their ways into Annkor's own systems. They pass on their information, and then take off for lunch at a new restaurant. Apparently, the restaurant works in reverse. They un-eat food and un-drink beverages and give them back to the servers. Weirded out, they leave.
Socrates whines so much about going to Sherman's lab that Calvin decides to just scan him with the MTM and take the report there instead. Annoyed at being left out, Socrates tricks Calvin into thinking that there is a huge prank that's been set up, causing Calvin to become super-paranoid. They still make it to Andy and Sherman's. The hamster looks over the report, and it seems the chip picked up a transmission from Annkor. MTM points out that Calvin thought the voice sounded familiar and suggests using a Mind Probe to figure out who it might have been. While they succeed in using it to get a complete of people who might be responsible, the after-effects give Calvin amnesia. He remembers Hobbes, but not Andy, Sherman or the MTM. Hobbes takes him home to recuperate.
Galaxoid and Nebular visit their friend Rowan, who works in the planet's security division. While they're chatting, someone on Annkor is plotting with someone off the planet to help them invade. They break through the transdution barriers, and an invasion begins. Galaxoid and Nebular, knowing that Earth has been invaded before, quickly send a message to Calvin and Hobbes.
Calvin's amnesia isn't improving, and Hobbes and MTM are arguing over how to bring him out of it when Socrates arrives. At first Calvin doesn't recognize him, but when Socrates drops hints about his big prank, the deep-seated fear of Socrates' pranks proves enough of a shock to bring Calvin's memories back, and he begins panicking again, until Socrates' chip receives Galaxoid and Nebular's message, crying out for help. Calvin agrees immediately to help, and he and Hobbes, along with a confused Socrates, collected MTM, Andy and Sherman, and they take off for Annkor, ready for a fight. They are unknowingly pursued by Holographic Retro.
The invaders are the Plantonians, a violent and wasteful race, who need a substance known as Jethrik to save their planet, having depleted and abused their own. Annkor is one of the few planets to have an abundant supply, so the Plantonians lay claim to it, causing massive destruction that is led by their leader, Commander Nesbin. Talks with King Stor break down, and the invasion becomes violent. Stor makes it to Galaxoid, Nebular and Rowan and hides with them, sorrowfully watching the war. Meanwhile, Nesbin and his assistant Ned search through the planet's archives, and they find the single prison on the whole planet. They need to rescue the one who helped them get here.
Calvin and the group arrive on Annkor and meet up with Galaxoid, Nebular, Stor and Rowan. They explain the situation, and Calvin deduces that the transduction barriers were taken down from someone on Annkor. They take note of a tiny object landing on Annkor on the radar, but ignore it for now in favor of finding Nesbin, who will lead them to inside man. Using the MTM to track him, Calvin takes off with Hobbes, Andy, Sherman, Socrates, Galaxoid and Nebular. The object turns out to be Holographic Retro's light bee. He sees them and follows them discreetly.
Nesbin and Ned find a cave and leave two snipers to guard the entrance. MTM detects them, and Calvin manages to talk them into standing down and leaving, terrifyingly so. They hurry into the cave, where they find a single cage. Nesbin has opened it, and out steps the human version of Retro, just as Holographic Retro catches up. Nesbin and Ned leave, and Human Retro tells our heroes what he's been up to: he's gone insane from being on an alien planet. Although he's ready to destroy him, Calvin manages to distract him by pointing out that Holographic Retro has abandoned all their original plans with the Imaginator in favor of some other ones. Retro in unimpressed and plans to switch his hologram off and start over, but the hologram flees. In the enusing confusing, Hobbes, Andy, Sherman and Socrates escape, while Retro steals the MTM. Calvin, Galaxoid and Nebular flee as well, but with a destination in mind.
Hobbes, Andy, Sherman and Socrates rejoin Stor and Rowan, who receive a message from Calvin, saying that he's going to the backwards restaurant to work on his plan. Reassured, Hobbes takes command, loading everyone into the box just in case they need to escape.
Calvin, Galaxoid and Nebular examine the backwards restaurant, figuring out how it works. It's actually encased in a concentrated time vortex, putting everything connected to it in a field of backwards-running time. Retro arrives and tries to destroy them with the MTM, but MTM plays a few mind games with him before Calvin tells him to use his Apocalypse siren, which effectively deafens Retro, causing him to drop MTM and run away. Calvin then uses MTM to copy all the data from the restaurant's backwards generator to a compact disc. They all run to Galaxoid and Nebular's hovercraft and set off, not knowing Retro is hanging onto the bottom. They meet up with Hobbes and the others, and then they find the Plantonians' mother ship. They are teleported aboard.
Calvin and Nesbin confront each other in the ship, but unknown to them, Holographic Retro stowed his light bee in his human self's lab coat, and he activates himself over Nesbin's head, landing on him and incapacitating him. While the two Retro's argue with each other, Calvin sneaks over to the mother ship's computers and downloads the disc, with the backwards software. The ship suddenly starts doing everything in reverse, causing it to return all the Jethrick they stole from Annkor. Calvin and the gang escape via MTM's teleporter, and Calvin uses the backwards software to send Retro back to his cage. He then reveals that when he got his memory back, he got a glimpse of the future: what they're seeing now - ships flying reverse.
Once Annkor is restored and all the damage is undone, they send the Plantonians back to their home planet (in reverse), and they set up the transduction barriers, keeping them out and effectively dooming their planet.
The entire planet thanks Calvin and Hobbes for their help, and after giving instructions to keep an eye on the human Retro, the gang take off back to Earth in the box.
- Alien Invasion: The main plot has a violent alien race invading another, much more peaceful alien planet.
- A Planet Named Zok: Annkor.
- Apocalypse How: Calvin claims a Class 1 will happen if Socrates' secret prank is unleashed.
- Ask a Stupid Question...:Hobbes: So... you remember everything now?
Calvin: No, Hobbes, this is just an amnesia spasm. OF COURSE I REMEMBER EVERYTHING NOW!!!
- Badass Boast: Calvin delivers one that the rest of the cast is legitimately impressed with.Calvin: Well, I have news for you! You're not taking a bit of Jethrick back to Planton V! But I do have something else you can take back to your people.
Nesbin: What's that?
Calvin: A word of warning! As long as the Supreme Earth Potentate is around, Annkor... is ... defended!
- Big "WHAT?!": Nesbin does one as Calvin puts his plan in action.
- Character Check: Calvin's Laser-Guided Amnesia ends up undoing most of his Character Development as well, leaving him with his original personality.
- Colony Drop: Downplayed and Played for Laughs - Galaxoid accidentally sends a satellite hurtling for Earth. Nebular is unconcerned.
- Continuity Cavalcade: The scene where the MTM uses the Mind Probe to search Calvin's mind is filled with one-off characters from previous episodes.
Suddenly a rush hit Calvin like a thunderbolt. In an instant he relived every single moment over from the point he and Hobbes flew into the pond on that winter day to the present moment. Retro Griffin reaching for him and Hobbes in the wagon with the claw car. Rupert firing his ray gun at him, Hobbes, Stupendous Man, Tracer Bullet and Spaceman Spiff. Him, Hobbes, Andy and Sherman running, terrified away from the Teacher Creature. The TV coming to life and attacking him and Hobbes. Yellowstone erupting. Dr Brainstorm arguing viciously with Jack, who remains bored. Holographic Retro attacking Calvin. Sheila holding up a chainsaw and laughing insanely. Jacqueline waving in a friendly hello. A disturbed ghost gasping desperately and crawling upwards towards him and Socrates. Installing the MTM's voice chip. Dr Thunderstorm releasing an army of Shadow duplicates onto the planet. The big prank Socrates was planning. It all came back to Calvin and hit him like a freight train.
- Also, when Calvin finally gets his memories back, this occurs:
- Continuity Nod: The amnesiac Calvin's last memory before sitting in Sherman's lab is basically the final strip.◊
- Crapsack World: Calvin claims this will happen to Earth while panicking.
- Enemy Mine: Holographic Retro briefly aids Calvin in fighting Nesbin.
- Eureka Moment: As Calvin stares at Sdrawkcab, he notices its smoke going inwards, pressed against some sort of wall, leading him to conclude it was because of a concentrated time vortex that the restaurant got its gimmick.
- Everyone Hates Mimes: Calvin claims that Socrates' prank will wipe out all mimes.
- Insult to Rocks:Sherman: Yeah, but then again, every member of that crew has the combined IQ of a raisin. And that's actually considered to be an insult to raisins.
- Large Ham: Lampshaded.Socrates: Why, Calvin, use your indoor voice.
Calvin: THIS IS MY INDOOR VOICE!!!
- Laser-Guided Amnesia: The Mind Probe ends up giving Calvin selective amnesia - he remembers Hobbes, but not Andy, Sherman, or the MTM.
- Long List: See Continuity Cavalcade above.
- Manipulative Bastard: Calvin.
- Medium Awareness: When Socrates' transmitter goes off:Calvin: Geez whiz, we haven't seen this for a couple seasons.
- Mind Probe: The MTM can use one, and Hobbes even references The Castellan's infamous line.
- Monster Clown: Calvin, while panicking, claims that the clowns will survive (though the mimes will not).
- The Mothership: The Plantonians have one.
- Noodle Implements: On Socrates' plan:Hobbes: But where are we going to get a medieval catapult?
Calvin: Or three grizzly bears?
MTM: And we're nowhere near Los Angeles.
- Not Allowed to Grow Up: Lampshaded hard."You know, I don't know how I dealt with you four years ago," [Hobbes] sighed.
"Four years!" Calvin gasped. "That would make me..... ten years old, now!!"
"Uh, no, Calvin," MTM said. "You're only six."
There was a pause while Calvin and Hobbes both mulled that around in their heads.
"....How is possible?" Calvin asked at last.
"Televison contracts," MTM replied. "Besides, this is kind of a scifi-y show. We'll think of an excuse, soon."
- Numbered Homeworld: Planton V.
- One-Word Title
- Sdrawkcab Name: The alien restaurant Sdrawkcab, where visitors essentially are given money and vomit up food and drink. Apparently, it got its start in a universe named Esrever.
- Shout-Out: Nebular watches The Astronaut's Wife, not understanding it, and Galaxoid mentions Old Yeller and Star Trek.
- Also, Galaxoid defends Independence Day to King Stor.
- A panicking Calvin demands that somebody call Oprah, the Sci Fi Channel, and Doctor Who.
- When the MTM suggests using the Mind Probe, Hobbes remarks "No! Not the mind probe!"
- Calvin, still panicking, believes that "giant Steven Spielberg-brand ''War of the Worlds tripods are going to shoot up from the ground and kill us all!!"
- At the very end, Calvin heads back home, not wanting to miss Tom and Jerry.
- Also at the very end, Calvin asks the MTM to put on some traveling music. He plays "Holiday" by Green Day.
- Take That!: According to a panicking Calvin, the only survivors of an apocalyptic Earth include Alexander Ludwig.
MTM: Oh, sorry about that, mate. I didn't hear you the first time. I was thinking about Family Circus. It was really funny today.
Calvin: Oh, that's a filthy lie. It's not funny at all!
"But there'll be aftereffects! The people of Annkor will suffer unless one of us stops this insane dig! A dig so incredibly stupid that it makes the Big Dig in New Jersey look smart and well-executed!"
- Also, this line from Calvin:
- Twitchy Eye: Galaxoid has one.
- Two of Your Earth Minutes: Inverted as Nebular says that Earth's rotation around the Sun takes one year, or seven loomres.
- Umpteenth Customer: Referenced as Galaxoid and Nebular receive money from Sdrawkcab:"Maybe we're the millionth customers."
- Wouldn't Hurt a Child: One of the two snipers follows this trope, but the other believes orders are orders. This is how Calvin manages to get them to flee.
- You Can Talk?: Lampshaded.Retro: You can talk?!
MTM: Last time I checked.
- "You!" Exclamation: Done twice as Retro is freed.