Billy & Mandy vs the Martians (The Grim Adventures of Billy & Mandy)

"Billy & Mandy vs the Martians" is the eighth episode in the fifth season of The Grim Adventures of Billy & Mandy.

Plot
When Billy destroys Grim's favorite childhood toy, Fancy Jake, Grim feels devastated and wishes he had never lost the limbo game that made him become Billy and Mandy's best friend forever and ever. A lawyer appears saying that although the game is legally binding while all parties remain on Earth, it is not if Grim leaves Earth.

Why It Rocks

 * 1) The plot is very nice and different here, as it has Grim leaving to go to space to gain respect for himself - which is a nice change to the show's tone.
 * 2) Some emotional moments, such as Billy begging Grim not to go to outer space and crying on his shoulder.
 * 3) The alien/zombie designs along with the Martian Grim Reaper (aka Emperor Mars) and even that one bug seen in the cave look pretty cool.
 * 4) Some funny moments, pop-culture references and even fourth-wall breaks, such as Billy saying "hey, this isn't Codename: Kids Next Door, when seeing an Earth hologram, the news reporter saying "this just in, the present has declared the state of National Pants Day! and Grim saying "Uranus", making Emperor Mars burst out laughing. There's even fourth-wall breaks where Billy says "this can't be where it ends!" and Mandy saying "it can't end this way!"
 * 5) * Speaking of which, the show had a crossover with Codename: Kids Next Door, though it wasn't well-received...
 * 6) The Braincaster sounds like an impressive invention with it not only brainwashing everyone in Endsville, but it even broadcasts people's thoughts to the zombies and keeps them in permanent states of mind control - as said by Emperor Mars. We also get to see all the other Reapers but in spirits due to them disintegrating.
 * 7) A bit of continuity is mentioned from the very first episode "Meet the Reaper", where Grim mentions to Emperor Mars about him becoming "friends" with Billy and Mandy after losing to them in a limbo game. And also from "Get Out of my Head", where Billy says to Grim "you can pick your friends and you can pick your nose, but you can't pick your friend's nose" - which was something Mandy as Milkshakes said to Billy at the end of that episode before scratching him.
 * 8) Speaking of which, Billy learns his lesson for destroying Grim's favorite toy and the watermelons by saying what Mandy said from that said episode along with listening to who they really are.
 * 9) Although becoming less likable later on, the Martian Reaper gets his comeuppance when getting sucked out of the spaceship and sent to another portal thanks to Billy pressing one of the buttons.
 * 10) Good Ending: After Emperor Mars gets his comeuppance as mentioned above, Grim lands back on Earth with Billy and Mandy and sit on the ground. Although she was only kidding, she did feel sorry for Grim not enslaving humanity and then we see Irwin still alive.

The Only Bad Quality

 * 1) Billy was still unlikable at the start for throwing watermelons and Grim's favorite toy on General Skarr and through some of the windows.
 * 2) * Likewise, Emperor Mars became less likable throughout the episode.