The more scooby snacks they ate the braver the got. Scooby-dooby doo uses the word dooby in his own name. I didn't even know there was a drug called scooby snacks.
And its variant, scooby snacks contain drugs. Thats why he has the munchies and he always sees the ghosts hallucinations before the others. Whenever scooby, or shaggy for that matter, eats a scooby-snack, they go ape.
Scooby is also hungry all the time. Oh, and they occasionally take some old guys mask off to solve a mystery. Thus explaining why when the mystery machine took off, smoke came out of it. Scooby and shaggy were willing to do anything for a scooby snack. The first one may be the only rumor on this list with some truth to it.
It may be a little hard to swallow, but just take a look at the evidence. It just blows their mind and they do whatever they are told, because they are so lit.