Author's Note: As a special Halloween treat, I present to you a Scooby-Doo / Undertale crossover in the style of the old The New Scooby-Doo Movies (1972-1974) and the new Scooby-Doo and Guess Who? (2019 - present). I hope you enjoy it. Also, for any of you dedicated Undertale fans out there, this takes place in an AU where Asriel Dreemur was permanently SAVED, turned back to normal, and reunited with his parents. No specific AU here, although it was heavily inspired by AbsoluteDream's Over the Void comics and art on DeviantArt.

So, without further ado, let's start the show!

Cold Open

Undyne seemed to be a monster of many homes. First was her original home, which went up in flames after a hangout gone wrong. Then, she briefly moved in with her best friend Papyrus and his brother Sans. And now, with the hated barrier finally broken, Undyne now lived in a nice new home up on the surface.

However, on this particular night, when the former Captain of the Royal Guard opened her front door and turned on the lights, her home looked quite far from nice. Undyne's jaw was dropped as she looked about the room at upturned furniture and items strewn about. She eventually closed her mouth so she could grind her teeth in rage. She stormed into the home and said aloud to herself, "You gotta be kidding me! Who or what is enough of an idiot to break into my house!"

Undyne glared about the ransacked home, stopping a moment to gaze at her old armor. The impressive suit of steel still stood right where she had put in on display a while back.

"Huh. Well, I'm glad they didn't touch that," Undyne remarked dryly, then she turned and said, "Well, I better check and see what they did steal."

As Undyne stooped down to check out a bureau that had been knocked on its side, all of its drawers pulled out and their contents thrown across the floor, she didn't noticed the eerie red glow that appeared in the armor's eye slits.

As she placed clothing and books back into the drawers, the sound of creaking metal caught Undyne's attention. She stopped and quickly turned around, only for her eyes to grow wide in disbelief as her armor towered over her, its arms raised and a menacing glare in its eye holes.

A demented maniacal laugh echoed from the suit of armor, and it swiftly turned and dived out a nearby window with a tremendous crash.

Undyne sprang up and dashed to the smashed window, looking out into the darkness in search of the specter. When she could spot no sign of it, Undyne could only say one thing.

". . .What?"

Scooby-dooby-doo!

And guess who?

We know you're one in a million (Scooby!)

Cause we can count on you!

Scooby Doo!

To catch and unmask that villain!