Scooby Doo Where Are You: Scooby doo can talk because we say so now shut up and watch the fuckin cartoon
The New Scooby Doo Movies: same
The Scooby Doo Show: same
Scrappy Doo: same
The 13 Ghosts of Scooby Doo: same
Boo Brothers: same
Ghoul School: same
The Reluctant Werewolf: same
What's New Scooby Doo: same
A Pup Named Scooby Doo: same
Zombie Island: same
Witch's Ghost: same
Alien Invaders: same
Cyber Chase: same
That one johnny bravo crossover: same
Live action Scooby Doo films: same
The /other/ live action Scooby Doo films: same
Every fucking adaption of Scooby doo ever: same
Mystery Incorporated: Scooby doo is the descendent of an alien race of godlike creatures called the annunaki that cross the barriers between our world and theirs every thousand years by possessing animals; any offspring sired by the annunaki and normal animals have near supernatural abilities such as amplified intelligence and the ability to speak human language which makes scooby part horrifying lovecraftian god from the dawn of time and that's why scooby doo can talk