The Scooby-Doo/Dynomutt Hour (1976)

S1E13 The Harum Scarum Sanitarium

While visiting Niagara Falls, the group finds themselves lodging at a haunted asylum, where the spirit of Dr. Coffin lingers. Two of his accomplices appear to be transporting patients in an ambulance, but it’s unclear whether these individuals are actually patients or if they are concealing a deeper mystery.