This is where any optional rules and related issues are discussed.
From the Risus Companion Boxcars and Breakthroughs: if you roll all sixes, you get to roll again and add that result to your roll. Keep doing that until you stop rolling all sixes. (This is where those single-dice cliches can really do some good.)
Eye of the Tiger: The players summon up a montage for a quick dice boost.