A/N: man I wish they could combine these shows together! It could be one of the best cartoon crossovers in history, like the "Jimmy and Timmy Power Hour" or "Mario and Sonic at the Olympics". I hope I did good cause tbh I'm not good at adult jokes. Enjoy the first chapter of a horror story!

People have many adventures of mysteries and romances. But sometimes it's best to stay at home where you are safe and protected from nothing of a powerful source. But we can't all be in safe conditions. Sometimes we're just invited in.
At the park from a very far distance from the town they lived in, the workers in the park were in their home sitting around watching a new horror movie that had just came out. 'Attitude's death'. The people who were just sitting around bored out of their minds were Mordecai, blue jay bird, and Rigby, the small raccoon. Pops was their buddy who was enjoying the lame horror movie. But who can blame a happy man like him. The other workers were a bit busy in their own time. Muscle Man and High Five Ghost were at home having a pizza party, which made a super big mess that they don't have to clean up, Thomas was out getting some coffee, and Skips was working out, of course.
"Good show!" Pops clapped as the movie went on. "Jolly good show!"
Right when they were about to reach a woman getting eaten, their boss of the park, Benson, had walked in with a envelope in his hands. "Mordecai, Rigby, turn off the TV and listen up."
They groaned and turned it off. Simply even more bored than before.
"Why are y'all complaining? You didn't even like that movie." Benson mention.
"There was nothing else we could do." Rigby spoke by laying his head back.
"Well now we do." He began to open the letter and read the message on the paper. "Two men name Luther Boon and Donald Logo invited us to join them and some other crew on a paranormal investigation this Saturday."
"Looks like Muscle Man is gonna have some more ways to scare Rigby." Mordecai laughed.
"Oh shut up man." Rigby said. "His pranks are way too boring to be frightening."
"Oh sure. Like last week when he-"
"STOP TALKING!" He interrupted his friend.
Benson only rolled his eyes and said "Enough fooling around. We're going to need a lot of cameras and some microphones."
"Why can't they just but the stuff?" Mordecai asked.
"Because they want to believe that ghosts and stuff only come around when you being your own materials."
"... well that's stupid."
"Oh! This is going to be so much fun!" Pops cheered with glee.
"So what ghost are we suppose to investigate?" Rigby asked.
"John Wayne Gacy Junior."
The bird and raccoon gasped. They couldn't believe their ears when that name was spoken. Their faces were terrified. Pops, on the other hand, just looked lost. "Who is John Wayne Gacy?"
The three gentlemen looked at him surprised. He is like super older than them and he doesn't even know? That was super creepy.
"You don't know who that is?" Rigby asked him.
He nodded.
"Well there's a good reason why Pops doesn't know." Benson said. "And it's best he doesn't."
"Well who is he? He sounds interesting."
"Pops, John Wayne Gacy was a man who loved to murder and molest young boys under the age of fourteen." Mordecai said. "He was very old back then and lived in the fifteen hundreds."
"Maybe." Rigby mention.
"Some say he died from an infection he got in his system." Mordecai continued to explain. "His house is still up and not destroy to this very day, but no one even dared to walk in the disturbing home."
Pops was a bit surprised by the story. His positive energy was still up but he had fear and images of how this man could have done such horrible things.
"Hey wasn't this guy a clown before?" Rigby asked his blue feather friend.
"Uh huh. That's how he use to grab little boys very easily."
"Do we have to investigate such a horrible history in a home?" Pops asked.
"Oh come on." Rigby said trying to cheer the pink man up. "This could be more fun than watching that boring horror movie."
"That is very true." Pops agreed.
"Well you better pray for your souls," Mordecai warned. "or he'll take them like how he put those young boys in his crawl space."
The raccoon and giant man were even more terrified.
"Way to make it more creepy Mordecai." Benson glared at him as he was smirking.
"I try."

Meanwhile...

The mysteries of this town was madness but was loads of fun for those who enjoy solving them. But no one seemed to love solving them, except for, Dipper Pines, and his twin sister, Mabel Pines.
The biggest mystery he has ever solved was that his own Grunkle Stanley had a twin brother too named, Stanford. It was a few weeks ago when they're discover the man from a portal that has been hidden for so long. It was now destroy but contain a powerful source still.
And today, it could be the ending of their lives when Saturday is being reach to them.
The family, including their friend, Wendy Corduroy, were sitting in the living room playing battle ship. "I'm gonna say D7." Wendy says.
"Miss." Dipper said placing his white dot.
"Miss for Mabel." Mabel said making his dots look like hearts.
"Aw man! She got me." Stanley pouted.
"Ha ha! In your face old man!" She cheered in victory.
"Don't make me fire you."
"Hey dudes!" They heard, Soos, their handyman, yelled from the hall. He came in with lots of mail. "Mails here!"
Everyone cheered, hoping that what they order was in. "Here you go Mabel for your hottest boys of the week magazine, Dipper for your paranormal thoughts magazine, Wendy for your teen mags, and mr. Pines for a bunch of letters. Me, I got my book for cooking sugar-flavored cookies! Oh and I got some letters for mr. Ford as well. I'll go give it to him." Her left to look for the mysterious man.
Dipper began to wonder about Wendy's mail. She doesn't live with them. "Why does your mail go to Grunkle Stan's?" He asked.
"Every time my family gets mail, my dad decides to throw it out. One time, he threw out my birthday cards." She said.
"Oh boy." Mabel said. "Looks like Gabe got some competition with a cuter boy. There's my husband." She pointed to the cute guy that Gabe was competing.
Stanley looked at his mail and saw it was nothing but a bunch of envelopes. One was for his brother for a money check. He discovered the family's mystery from a few weeks ago. He only glared and threw it away. Then he pulled out another envelope and saw it looked pretty interesting. He open it and read it quickly. "Check this out. Some losers wants us to join them on a paranormal investigation this Saturday."
That certainly got everyone's attention right away.
"A paranormal investigation?" Dipper was getting excited.
"Yeah. I mean, what kind of werid I decides to go to some fake ghostly adventure just to catch nothing?"
But his answered was from Dipper as e grabbed the envelope from his great uncle. "I would!"
"Me too!" Mabel cheered.
"I like to go." Wendy said standing up with the twins.
"Oh sure, I'll let y'all go to see that all scary stuff that happens us all fake." Stan rolled his eyes.
"What's the investigation ghost ma-gig?" Soos asked.
"Some one named John Wayne Gacy Junior." Dipper read on the letter.
The two workers gasped and Stanley looked shock and spitted out his pitt cola. The twins did not understand what was so wrong with the name.
"What's wrong?" Mabel asked.
"You mean you guys don't know?" Wendy said.
They nodded together.
"Oh no!" Stan said quickly standing up. "You two are forbidden to go to that haunted place!"
"Why?" Dipper asked. "What is so terrible about this guy?"
"Well-"
"Nope! You two are never allow to tell them who this man was!" Then he looked at his niece and nephew. "And you two are never going! Never in a million years!" Then he left the living to calm himself.
The twins looked at their two friends and Wendy pointed to the window.
Soon the workers and twins were outside of the Mystery Shack, very far away from it so Stanley wouldn't hear what Soos and Wendy were gonna tell them.
"John Wayne Gacy was a horrible man." Wendy started off. "He use to take little boys and murder them for fun. He always used a clown costume as a disguise. The guy died from having a heart attack is what some people say. He was old back in the fifteen hundreds."
"I was so frighten of the stories, I couldn't sleep in my bed alone for a week." Soos said.
"So how come Grunkle Stan didn't want us to go?" Mabel asked.
"Well I guess you can say that he doesn't want you two to get hurt. Especially Dipper." Wendy mention.
Dipper wonder why mostly him. Obviously Stanley doesn't show much proudness of Dipper than he does with Mabel. "W-Why me?"
"Because-"
Wendy stopped Soos from talking. She didn't want Dipper or Mabel to discover what he use to do BEFORE he killed them. "It's best not to know."
"The point is that you're all going to need cameras."
They turned surprise by the agreement of going. They almost mixed him up with Stanley. Luckily they were able to discover it was their other Great Uncle Stanford.
"Wait, what do you mean?" Dipper asked him.
"I mean that you're going to need lots. In my opinion you should go. It's another mystery that should solved."
"You mean we can go?" Mabel asked.
"Yes you may. Just gotta make sure Stanley doesn't suspect a thing and you'll have to pretend like you're all going for a sleepover in the woods."
"Awesome! Can Candy and Grenda come too?"
"Sure dude!" Soos agreed.
"I don't think that's such a good idea." Dipper differed.
Mabel looked so surprised at her twin. Not normal for him to say that. "Why not Dipper? They're my best friends. Plus we barley spend time together."
"Well Mabel, no offense, but you do know all Candy and Grenda are gonna do if goof off?"
"No they won't. They're serious... most of the time..."
"Exactly."
"Please Dipper? If they come on this trip with us, I promise I won't invite them two anymore of our adventures together. Please?"
Dipper really didn't want those two girls to come along. He knows them, even though they're not close friends like they are with Mabel. There's gonna be nothing but talking about some cute boys on their adventure. But if this was gonna be the last time, it shouldn't be a problem. Right? And he loves seeing his sister happy on some levels.
He sighed and smiled. "Alright. They'll come."
"Yes!" She hugged him tightly. "Thank you bro bro! And since we're going to need cameras, Grenda's mom has a few we'll need."
"And I have some night vision cameras and energy indicators in my basement." Stanford said with a smile.
"Sweet dudes!" Wendy said. "Be prepared for the haunted home this Saturday!"
"Hey wait." Dipper turned to his other Great Uncle. "Why don't you come with us?"
"I loved to," he said. "but someone's gotta keep an eye on Stanley, in case he searches for you. Besides, I know you guys will do great."
"Well alright." Dipper felt better with his uncle's honest words.
"Just make sure Waddles goes to bed around ten." Mabel mention.
Then Stanford laughed at his silly niece. "Duly noted."

A/N: understand please that John Wayne Gacy is evil and hope he burns in hell! Anyways thanks for reading the first chapter and hope you're ready for the next one! Bye bye!