The Scooby-Doo Show

A Highland Fling with a Monstrous Thing (3x6)

Air date: Oct 14, 1978

The gang heads to Scotland to help Velma's friend Aggie MacDuff, who's ancestral castle home, which she's turned into a tourist attraction, is being haunted by the ghost of her great grandfather Finnyan MacDuff, who in turn has summoned the Loch Ness Monster to help him scare away potential tourists.