Fred, Velma, Walter and Jane rushed over to a stunned Mondavarious. Velma tried taking the Daemon Ritus from him, but as she touched it, she flinched back in pain like it had burnt her hand.
"You okay, Velms?" Jane asked her.
That's when Fred noticed something...
"Hey, look, guys..." Fred pointed out to a cut in the man's neck.
"A man in a mask" Walter said.
Fred grabbed the mask and pulled it off, revealing Mondavarious to actually be... a robot!
The whole gang looked shocked as they watched the robot's chest burst open, revealing to be none other than...
"Puppy power!" Scrappy Doo exclaimed.
"You've got to be kidding me" Cynthia kinda grumbled.
"Scrappy Doo" Velma said in shock, while she and the rest of the gang couldn't believe their eyes.
"Correction: The new, improved Scrappy" the great dane puppy proclaimed while strangely, his body started to change dramatically. "Because I, Scrappy Dappy Doo, have absorbed enough energy, to rule the world with my all-powerful army!"
The gang started to back away in fear, while Walter had a protective hand in front of the kids, as Scrappy continued growing as big as a dinosaur.
"And I've brought you here, puny, pathetic Mystery Inc, to witness my moment of triumph" Scrappy told the gang. "All I need to complete my transformation is..."
Scrappy finally finished his transformation into a giant, hideous monster. Scrappy-Rex.
"SCOOBY DOO!" Scrappy-Rex's voice suddenly sounded very booming and threatening.
"R-re?" Scooby gulped, shivering in total fear. "Ron't rou rean Melvin Doo?" he pointed over to that weird college student.
"SEIZE THEM!" Scrappy-Rex ordered his guards, as they started surrounding Scooby and the gang.
"Uh, oh!" the adventure kids gasped.
"Like, let's get out of here!" Shaggy told Scooby and the kids.
"RUN!!!" Kali yelled out to her friends, and the adventure kids began running away with Scooby and Shaggy.
Scrappy-Rex then hit Fred, Walter, Velma and Jane, far back against the walls. "Take that, pretty boy!"
"This is by far the most terrifying thing in my life!" Brock cried out in total panic and fear.
"I swear, I had a dream like this once!" David added in the same manner.
"Don't talk now, just keep running!" Teeders turned back to the boys.
"Guys! I got a plan to defeat Scrappy!" Kali called out to the gang.
"How?" Ann asked her sister, seeming a bit unsure while they kept running for their lives.
"Just follow my lead" the adventure girl instructed her friends, then took off running faster in front of them.
"Oh, I hate when Kali does this during a life-or-death situation. She's so simplistic" Cynthia groaned while she kept running with the others.
"Like, this is totally un-groovy, guys!" Shaggy said to the adventure kids and Scooby as they kept trying to get away from the giant, monstrous puppy.
"Scooby Doo, where are you?!" Scrappy-Rex taunted.
Daphne had finally made it up to the roof where she ran over to pull back the lever and open the air vents, but she wasn't alone. Zarkos was there and started attacking her. Luckily, Daphne avoid the attacks and began fighting back, using her marital arts and karate moves to good use. No longer being the damsel in distress.
Scooby, Shaggy and the adventure kids kept screaming and running away as Scrappy-Rex stomped after them.
"Yield to my puppy power!" Scrappy-Rex was right on top of them.
"We gotta tip over the protoplasm vat" Velma told Fred, Jane and Walter urgently.
"How?" they asked.
Velma quickly looked around and noticed Tauna's pincer. "The pincer. Come on!" she started running with Jane right behind her, only for the girls to be grabbed by guards.
"Hey, let go of her!" Walter snarled, glaring towards the guards as they had his wife and lunged at them.
Fred spotted the bungee cords on the ground and decided to use them for weapons, knocking the guards out with them and saving Velma.
Walter tackled the guards aggressively and had knocked them out. No one was going to dare hurt the love of his life.
"My knight in shining armor" Jane smiled dreamily to the man she fell in love with back in high school, having saved her life.
Walter and Jane looked to each other, about to have one of those lovely, romantic moments until Velma suddenly broke them up.
"Uh, I hate to ruin a tender moment, but we still got to save Scooby and the kids" the brainy girl reminded the couple.
Walter and Jane then looked back over in worry, seeing Scrappy-Rex now going after Kali.
"Scrappy, don't you dare touch my little girl!" Walter warned the crazed puppy if he even dare hurt his daughter.
But Kali was fine and not even worried while she was being chased by the monstrous puppy. She and the other adventure kids had been running all around Scrappy-Rex in zig-zags, keeping him distracted. The twins even ran through right under his legs, catching the monster puppy off guard as he quickly turned around to grab them, but lost his balance due to his giant size and fell hard to the ground.
The adventure kids regrouped and all high-fived each other in victory. But Scrappy-Rex got back up and roared in their faces, causing them all to flee rather quickly.
Scrappy-Rex then went back to chasing Scooby Doo.
"Scooby! Get Scrappy to come over here!" Kali called out to the great dane, pointing out to a big chasm area she was standing right over.
Scooby followed the tomboy's instructions, but ended up getting caught by Scrappy-Rex.
"You look so much bigger on TV" Scrappy-Rex stated to his uncle, while he had him in his grasp.
Scooby however, suddenly grabbed onto his nephew's snout, making Scrappy-Rex drop Scooby and let out a big disgusting sneeze, getting snot all over Scooby.
"Ew! Gross!" Cynthia and the twins cringed as they watched poor Scooby get covered in puppy monster snot.
The kids ran up to Shaggy, when they looked back to see Scrappy-Rex about to pound Scooby into the ground.
"Like, we've gotcha, Scoob!" Shaggy grabbed onto his buddy, as he and the adventure kids took Scooby down with them into the chasm.
"That was a close one" David sighed in relief.
"Come back here, you lazy beatnik!" Scrappy-Rex tried to get the gang down in the chasm, but obviously couldn't due to his giant size.
"I think we're safe now" Teeders told the gang.
Suddenly, Mary Jane appeared out of nowhere, surprising the gang. She then grabbed Scooby and Shaggy in a choke hold and held them up against the wall.
"You were saying?" Cynthia narrowed her eyes at Teeders.
"Crud..." Shaggy choked.
"We told you so!" the adventure kids glared to Shaggy.
"Reah!" Scooby added, glaring to his master.
Mary Jane then released her breath onto Shaggy, sending him into a phase of attractiveness for the pretty blonde girl.
"Give me the dog!" Scrappy-Rex ordered, and Mary Jane handed Scooby over to him.
"Scrappy, down! Sit! Bad Scrappy!" Scooby scolded his nephew, flicking him on the nose, only to cause the monstrous puppy to yell in his face.
"Let's finish this puppy! NOW!" Scrappy-Rex ordered, holding Scooby up to the pincer to take his protoplasm.
Meanwhile, Daphne had been caught by Zarkos, who was about to finish her off. But Daphne wasn't going to lose this time and bit Zarkos fingers, making him cry out in pain and let her go.
Daphne threw some karate kicks right into the Mexican wrestler's face, sending him down through the air vent hatch and falling onto the vat, making it tip over and release all the remaining protoplasms.
All the protoplasms flew around, returning to their own bodies and soon making the monsters appear. Daphne quickly then released the disco skull, having it reflect the sunlight from it and the monsters all exploded within seconds.
"Wahoo! We did it!" the adventure kids came back up out of the chasm just in time to see Scrappy-Rex's demolish.
"Mystery Inc., this ain't over!" Scrappy-Rex declared, storming over to the gang with Scooby still in his grasp. "I'll rock you and sock you! And crush you like!-"
Scrappy-Rex was then tapped on the shoulder, getting his attention to turn around and see Shaggy at the controls, with the adventure kids by his side.
"Like, dude?" Shaggy asked Scrappy-Rex.
"WHAT?!" the monstrous puppy growled at him.
"You're a bad puppy!" Shaggy suddenly sent the pincer to grab the Daemon Ritus, pulling it off Scrappy-Rex's chest and making the puppy return to his normal size.
"That's the end for you, Scrappy Doo!" the adventure kids glared down as they came over to the annoying puppy with Scooby.
"Come on, I can still take you!" the scrappy puppy glared to his uncle. "Put them up, you mangy mutt!"
"Could someone please shut that rat up!" Ann was annoyed, having her hands over her ears.
The adventure kids and Scooby had enough with Scrappy's chatter and Scooby kicked his nephew against the wall.
"Thank you" Ann told Scooby.
"Is that all you got?" Scrappy asked his uncle.
Scooby just shrugged his shoulders with a small smile, while the adventure kids all gathered around and gave the great dane one big group hug, having saved the day.
Everyone celebrated as everything was finally back to normal. Mystery Inc couldn't have done it without their teamwork. Jane and Walter shared a kiss, being a couple and all, obviously. But the adventure kids looked over and noticed Fred and Daphne were only talking to each other.
"Oh, kiss her already you ninny! For heaven's sake, while we're still young here!" Cynthia told Fred annoyingly, while she was watching with the other adventure kids.
Fred and Daphne glanced to the kids, then blinked to each other while they both blushed slightly. But soon, they did kiss, like the couple they were meant to be.
The adventure kids smiled to this then left them alone, deciding to go over and see Shaggy.
As they were talking to each other, they heard a strange sound and looked around. They soon discovered it was coming from a secret hatch door and opened it up. A familiar man with a long bread then climbed out. It was the REAL Emile Mondavarious!
"Wha?..." the kids had no idea what to think.
"Mr. Mondavarious, is that you?" Shaggy asked.
"Ah, yes!" Mondavarious climbed up out of the hatch and shook Shaggy's hand. "Oh, thank goodness! Thank you!"
"What happened to you?" Brock and the other adventure kids asked, while looking oddly at the man.
"Two years ago, that little pest turns up at a casting session for our evil elves" the real Mondavarious explained, referring to Scrappy. "Next thing I know, I'm stuck in a hole and he's cavorting about in a mechanical version of me"
Shaggy and the kids gave Mondavarious strange looks.
"But look, thank you so much! What a delight!" Mondavarious hugged Shaggy, nearly suffocating him before he let him go and left. "Fantastic! Fantastic!"
"That was weird" the adventure kids thought while they looked at each other.
Scooby was searching around through the happy crowd, when he soon found the one human he was looking for.
"Raggy!" Scooby cried out and ran to his owner.
"Scooby Doo!" Shaggy cried happily, and Scooby knocked him over, licking his face. The two best friends were happy to be reunited.
"I rove rou, Raggy" Scooby told his best friend.
"I love you too, Scoob" Shaggy smiled back to his best buddy.
The adventure kids smiled, happy to see Scooby and Shaggy together again, then came up to give the great dane another hug.
"Well done, Scooby" Kali told the great dane while she hugged him. "You're a real hero"
"Raw, rucks" Scooby blushed slightly.
Mary Jane came over, now back to normal, and thanked Shaggy, and Scooby for saving her life.
The rest of the Mystery Inc gang soon came over to Shaggy, Scooby and the kids.
"Mom! Dad!" the Harpercop siblings ran up to hug their parents.
The whole gang soon came together in one big family group hug, all happy together, having saved the day.