Scooby-Doo and Scrappy-Doo (1979)

The Scarab Lives! - S1-E1

Plot hole: There is a "scarab alarm" when the blue scarab arrives, Shaggy even comments on hearing this. The problem is, The Blue Scarab is a comic book, so the villain and Shaggy wouldn't know what the Scarab alarm sounded like.

Dan Moat

I Left My Neck in San Francisco - S1-E10

Other mistake: The whites of Scrappy's eyes are briefly the same color as his hair at the theater.

Rob245

The Hairy Scare of the Devil Bear - S1-E8

Character mistake: Velma says bears only have four claws. Wrong, they really do have five claws.

Rob245

Twenty Thousand Screams Under the Sea - S1-E9

Plot hole: During the diving contest Tiger Morris, who's posing as the sea monster, fakes his cries of terror and flees off to the left of the ocean. Then, seconds later he's suddenly back as the sea monster. Impossible for him to get into disguise that quickly.

Rob245

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.

Rob245