The Private Eyes(1980)
This old-dark-house spoof finds Inspector Winship (Don Knotts) and Dr. Tart (Tim Conway) summoned by Lord Morley to his mansion to reveal who killed him. Yes, you read that correctly. Unfortunately, Winship and Tart are The Yard's most inept detectives, and all of Morley's staff seem to be completely insane.
This was the first film released by Tri-Star Pictures. A follow-up film featuring the Wookalar monster was planned, but never made it to the screen.
This promo for an HBO airing of the movie was originally posted to YouTube by lugnut0.
This trailer was originally posted to YouTube by zoinks3.