Analyzing film genres and their Conventions

For my film opening I have decided to make it a Comedy Mystery. Here are some examples of Comedy Mystery films which I'd like to emulate in my opening:

• Clue (1985)
• Mystery Team (2009)
• Scooby-Doo (2002)
• The Cheap Detective (1978)
• The Pink Panther (2006)

The common conventions which we notice in all these films is that although a serious crime has been committed, in order to keep a certain lighthearted, comedy theme throughout the film, a ditsy, clumsy and somewhat unprofessional detective is used. By doing so, we almost lower our expectations of the detective and not expect him to succeed in his task, however when he finally does, it comes as a shock to us all.