The Scary Sky Skeleton - S1-E6
Audio problem: During the gang's ride on a bumpy road Fred warns Shaggy, Scooby, and Scrappy about some more bumps coming up. He's interrupted when they hit the bumps, then the word "bumps" comes out of Scooby's mouth.
Scooby-Doo and Scrappy-Doo (1979)
1 mistake in The Scary Sky Skeleton
Starring: Don Messick, Casey Kasem, Lennie Weinrib, Heather North
