I am stuck on what seems like a 5-year cycle, and at each rotation I have vivid memories of a film from my childhood that I desperately want to watch, but cannot find no matter how hard I look. I always watch a handful of promising leads, but none of them scratch the itch. Please help me if you can!

Things I remember for certain:

1. Haunted mansion setting, foggy dark spooky smoke-machines, lightning, etc.
2. A pair of bumbling detectives, at least one with a fedora… this is when I always think it was Abbot and Costello, but it couldn’t be…
3. At some point in the movie, these two encounter somebody digging for worms in a garden outside the mansion at night. Later, they find that person dead in the garden, buried in the ground with his feet sticking up, and one of the detectives makes a comment about how big the worms must have been… later, when they are back in the garden, the body has disappeared!

Things I believe I remember, but may be wrong about?

1. The movie was kind of a haunted mansion spoof, a comedy more than really scary?
2. They may have encountered a number of Universal-esque horror monsters (werewolf, mummy, Frankenstein’s monster etc.) during the course of the film?
3. I remember my parents renting it for me on VHS when I was home sick from school, and they generally prohibited scary/violent movies in my youth, so it must have been a PG film?
4. I am nearly certain it was in color.

Any ideas? It really drives me bonkers not being able to find this film!