Scrappy Doo, Doggie Do:
Scrappy Doo and his mad scientist Professor Vladimir Plum had been transferred to Townsville prison where he made friendships with many of the Townsville villains especially Mojo Jojo. He'd told Scrappy Doo that he wanted to seek revenge on the power puff girls. He also told Scrappy Doo that in Townsville Museum there was a statue of a canine head and that when the ruby gems were inserted into the statue it could transform all humans into dogs.
After hearing Mojo Jojo's tale of the canine head statue Scrappy Doo decided to steal it and turn the Mystery Inc gang into dogs as well as the whole world.
So that night Scrappy Doo, Professor Vladimir Plum, and Mojo Jojo escaped from Townsville prison and headed to Townsville Museum and stole the canine statue along with the ruby gems and went back to Mojo Jojo's lair.
The next morning the Mayor of Townsville had been advised by the police chief to contact Mystery Inc gang who consisted of Daphne, Fred, Scooby Doo, Shaggy, and Velma to solve the crime as well as assisting the power puff girls.
Meanwhile back at Mojo Jojo's lair Scrappy Doo, Professor Vladimir Plum, and Mojo Jojo set up the statue by putting the gems into the statue's eye holes and the statue began beaming rays out of it's eyes transforming humans across the globe into dogs. Scrappy Doo, Professor Vladimir Plum, and Mojo Jojo began cackling evilly. When suddenly the Mystery Inc gang and the power puff girls appeared. Scrappy Doo aimed the statue at them and transformed them into dogs. While the power puff girls dealt with the guard dogs. Daphne, Fred, Scooby Doo, Shaggy, and Velma tried to dislodge the statue from Scrappy Doo and Mojo Jojo's grasp.
The statue soon fell from their reach and smashed and all the humans including the Mystery Inc gang, and the power puff girls transformed into their normal humane form. Mojo Jojo and Professor Vladimir Plum had now turned into dogs and along with Scrappy Doo they were sent back to Townsville prison.