Audio problem: At the end of the show when Alice is blowing the whistle, the whole family comes to the top of the stairs. Mike says "Alice, it's 6 o'clock in the morning" Watch his mouth. It looks as though he curses and the (curse) word was dubbed out.
Continuity mistake: Scooby finds a clump of ape hair stuck in the wine cask. It cuts to the gang, then back to the cask as they walk up and suddenly the clump of hair is twice as thick. (00:16:45)
Continuity mistake: When Dum-Dum cuts the rope releasing Chug-a-Boom from the balloon, we cut to the car and you can see Clyde and Dum-Dum are surrounded by the rest of the Ant Hill Mob, but when we see the two in the next shot, the other members are nowhere to be seen.
Revealing mistake: In the song "Living Island", we see Judy frog jumping over Pufnstuf. When she goes back down, the wires holding her up and putting her down are visible.