A corollary to Finagle's Law which seems to have almost infinite applications in writing comedy:
Never attribute to malice that which can be adequately explained by stupidity.
Ignorance of Hanlon's Razor is one of the more common forms of Genre Blindness. However, applying the Rule of Shades of Grey ("No rule is universally valid, including this one"), Hanlon's Razor is often stated this way:
Don't assume malice when stupidity is an adequate explanation. At least, not the first time.