Clicking on various features not only initiates some simple animation but it propels a typical mission which includes a tribble infestation, a "redshirt" bemoaning his fate, beaming down to a planet to fight a fierce alien and besting him with a make-shift hand cannon cobbled together with "found" objects.
It's only replacing the usual Google logo for a day so I'll link the pic above to the doodle once Google saves it to their archive.