A Night of Fright is No Delight Scooby Doo, Where Are You! : Season 1 Episode 16

Scooby-Doo inherits a mansion after saving Colonel Beauregard Sanders from drowning some years ago. He and some other heirs will each get a fortune if they stay the night but there's a warning that the house is haunted. The warning appears justified when someone (or something) comes to frighten the heirs away.