It's troubling to consider that many writers "write what they know", and thus the only knowledge the handful who came together to write this particular episode of "Scooby-Doo, Where Are You!" had about clowns was that they hypnotized people and threw darts at them. Those weren't bright and sunny childhoods, that's for sure.
Writing this the idea arose to put listener's minds at ease by assuring them that ultimately the clown that appears in this episode is harmless, but that really couldn't be further from the truth. This one definitely not only tries to murder four teens, but their dog, too. But hey, at least he's not trying to eat them.