Disclaimer: I do not own Invader Zim, The Grim Adventures of Billy & Mandy, or any of the following characters.

Chapter 1

Squashed between Billy and Mandy on the former's couch, Grim had been lulled by the sounds of the B-grade horror film they'd stumbled upon while flipping through channels; the flickering light of the TV, casting shadows on the walls.

"Grim..." Mandy handed the skeleton her empty glass. "Refill."

"Why don't you get it yourself?" Grim chanced, knowing it was the wrong thing to say when Mandy sent him a death glare that put his title to shame. "Oh, alright. Whattaya want?"

"Dr. Pepper. Hold the ice."

Grim snatched the glass from Mandy's hand, and shuffled reluctantly toward the kitchen; cloak tail dragging behind him. "Why do I let a little girl boss me around, like that?" He muttered to himself, opening the fridge, and surveying its contents. "I'm the Grim Reaper, for cryin' out loud." As pathetic as it sounded, though, it was easier to understand if you knew Mandy. Her own parents were terrified of her. "Here's your—" Grim nearly spilled Mandy's drink upon returning to the living room. "Billy, wait...! Don't take me scy—!" Before Grim could finish his sentence, Billy had already disappeared into the swirling, green vortex he'd opened; igniting very real flames in Grim's eye sockets. "If you didn't have me scythe, I'd let you fend for yourself, wherever you are!" He yelled into the portal.

"We'd better hurry before it closes," Mandy said, hurrying after her friend. Grim sighed, following suit.

Aside from Dib Membrane, the hallway was predictably empty, when space appeared to rip apart before his very eyes, creating a tiny black hole, which happened to spit out three people. Well, two people—a young boy and girl—as well as what appeared to be the Grim Reaper. The boy emerged first, and took off down the hallway, leaving the other two scratching their heads.

"Hey, you, with the big head," said the girl, whose short, blonde hair was styled into devil horns. "Have you seen a boy with a scythe around anywhere?"

"He ran that way." Dib pointed. "And I don't have a big head!" He called after them, as they took off down the hallway, in the direction the boy had run. "No one will ever believe me about this," he muttered pessimistically to himself.