The Private Eyes (1980)

Two American detectives, Don Knotts and Tim Conway, who work for Scotland Yard are called to an expansive manor house to investigate the murders of its owners. It’s essentially an extended episode of Scooby-Doo where Scooby and Shaggy are replaced by these two comic greats. The story’s pretty predictable and it doesn’t feature the bungling duo in their prime, but it’s still fun and appreciative for being the last lead role pairing of the two.