The Grim Adventures of Billy and Mandy Wiki
The Grim Adventures of Billy and Mandy Wiki
Billy & Mandy vs. The Martians
Billy & Mandy Vs The Martians.png
Series The Grim Adventures of Billy & Mandy
Season 5
Production code 508
Writer Maxwell Atoms

Nina Bargiel Jeremy Bargirl

Broadcast information
Cartoon Network US Premiere March 23, 2006
Chronological information
Pandora's Lunch Box
Dumb-Dumbs & Dragons

Billy & Mandy vs. the Martians is a double length episode and is the eighth episode of season five of The Grim Adventures of Billy & Mandy.


Grim finally gets sick of Billy and Mandy after they destroy his favorite childhood toy, Fancy Jake and wishes to leave them for good. Just then, Morg, a Martian disguised as a human tells Grim that his deal with Billy and Mandy only applies on Earth, and if he leaves the planet, he doesn't have to be their friend anymore.

Grim then travels to Mars with Morg, however he left his trunk at Billy's house. Billy, Mandy and Irwin notice this and hide inside the trunk waiting for Grim to come back for it and take it to Mars, so they can convince Grim to come back to Earth. The trunk is put on a small space ship. When Billy, Mandy and Irwin are on the ship, they accidentally fall out, forcing them to walk to Morg's base. On the way, they find a Martian animal which helps them fight the martians by eating them, Billy names the animal "Admiral Wolverine Lightning Bolt".

When Grim and Morg are settled on Mars, Morg tells Grim about his Martian zombie slaves and how he is the ruler of Mars. He then tells Grim they could do the same (the same thing that turned everyone to zombies) to Earth, so they can rule the galaxy together. Morg tells Grim they could rule Earth using the Brain Caster, which is a machine which can only be powered by the stupidest and most distracted of minds to turn everyone to zombies. At first, Grim is reluctant to do so, but then Morg reminds Grim of how badly Billy, Mandy, and Irwin treated him, which convinces Grim to conquer Earth.

After that, the aliens invade Earth to find a person with the right brain for the Brain Caster. While this is happening, Billy, Mandy and Irwin find their way on to Morg's base. When they do, they find out Earth has been invaded.

After a while of testing for the right brain for the machine, Grim suggests that Morg should just find Billy and use him for the Brain Caster, but Morg ignores Grim and tells him he should stop thinking about Billy and Mandy. After this, Morg suggests they take a break from trying to find the right brain and play a board game instead. He tells Grim to go to the door next to the one marked "forbidden". Grim choose a board game, but then decides to look in the door marked forbidden as well. To his surprise, he finds out there are jars with ashes and scythes of destroyed reapers from other planets (they were destroyed for not following along with Morg's plans). Morg finds Grim lurking in the room and tells him the other reapers died by accident, and he should forget this room. Grim pretends to agree and makes it look like he will still work with Morg.

After this, Billy, Mandy and Irwin take a martian spaceship and they go back to Earth, but when they get there they are raided by martian zombies and are taken back to Mars, so Morg can use Billy for the Brain Caster. Morg banishes Mandy and Irwin to a pit were monstrous bugs like creatures try to eat Mandy and Irwin. Mandy is saved by Admiral Wolverine Lightning Bolt, but sadly, Irwin gets eaten by the monster.

During this, Billy talks to Grim about friendship, which makes him see the error of his ways and realize that the kids do in fact, care about him. Grim goes to save Mandy and Admiral Wolverine Lightning Bolt from all the zombies and Billy overpowers the brain caster causing it to break, this makes any of the zombies that were created from Billy's brain turn back into normal people.

Grim and Mandy come back to Morg's base and try to get him to become Grim's slave. Unfortunately, Billy sends him though a tube which blasts him off Mars and into deep space. Back on Earth, Grim makes up with Billy and Mandy, and Irwin comes back stinking with flies flying around him, Mandy asks how he survived because she saw him get eaten and he replies "Don't think about it too hard".


  • Story by: Maxwell Atoms and the Bargiel Brothers
  • Storyboard by: John Bahn and Mike Diederich
  • Directed by: Juli Hashiguchi and Eddy Houchins


  • Morg: You! But I fought... But how?

  • Beetle: Oye, flesh!
  • Irwin: (Screams)
  • Beetle: (Screams)

  • Mandy: I was wondering when you showed up.
  • Grim: Look out!

  • Mandy: I know you come back to us, Grim.

  • Billy: Admiral Wolverine, where have you been?

  • Irwin: Here I am.

  • Mandy: But I saw the beetle swallow you how did you escape?
  • Irwin: Don't think about it too hard. 


  • The title card makes a similar reference to Moron Mountain, a theme park attraction run by Mr. Swackhammer from the animated film Space Jam.
  • While inside Grim's trunk, Billy stats that it's bigger on the inside, as a reference to the TARDIS from Dr. Who.
  • When Billy first enters Morg's base, he says "Hey, this isn't Codename:Kids Next Door",before stating that the base it's just as mesmerizing. This is the second time that KND was refferenced before the crossover, the first being "Sickly Sweet".
  • It is revealed that there is actually more than one reaper in the universe. Apparently, every planet in the solar system has its own reaper (i.e. a Martian reaper), some of which got killed by Morg.
  • When Grim suggests to use Billy to power the Brain-Caster, Morg asks who he is, which doesn't make any sense since he literally said Billy's name when he convinced Grim to conquer Earth.
  • In space, Mandy, Billy and Irwin weren’t wearing spacesuits and managed to survive.
  • When Billy states, "You can pick your friends and you can pick your nose, but you can't pick your friends nose." This is a quote stated by Mandy in "Get Out of My Head”.
  • End Credits: Billy and Irwin were somewhere half naked and Billy's bread turn out to a harry monster and attack Irwin. Billy ran for his life and the monster got off Irwin and he said "Taste Like Chicken".


Billy & Mandy vs. the Martians/Gallery



Billy and Mandy - S6E08 - Billy & Mandy vs the Martians