Ed Piskor, creator of the Wizzywig comic, sez, "This article contains a dozen or so examples of comic panels that handle sequences of different related actions. Usually action is broken up through a series of panels, or even pages, but master cartoonists are able to handle a lot of information within a single illustration as evidence at the link. Good examples are hard to find."
The Art Of Cause and Effect In A Solitary Comic Panel
(Thanks, Ed!)