This is SO cool. Unmannedspaceflight.com member Astro0 was fiddling around with an interesting-looking sequence of Cassini images when he discovered their purpose -- they were gathered in order to see if Cassini could catch aurorae flaring into being near Saturn's north pole. Cassini sure did! The animation is absolutely incredible. I've just posted a brief excerpt below to give you a bit of the flavor; download the full version to be mesmerized by spinning Saturn, streaking stars, and sudden auroral flares that rotate as they fade, floating above the visible edge of Saturn's disk.
NASA / JPL-Caltech / SSI / animation by Astro0, unmannedspaceflight.com
Saturn's rotating aurora (excerpt)
This animation consists of 21 frames captured by Cassini on October 7, 2009, focused near Saturn's north pole on the night side of the planet. Each frame is a long exposure, causing background stars to extend into long streaks. There are other small pointlike image artifacts that do not move from frame to frame (so they are most likely hot pixels or some other sort of thing internal to the instrument). There are also occasional cosmic ray hits that produce one-time streaks that aren't visible in subsequent frames. As Saturn rotates, the aurora flares. This is just an excerpt of a much longer animation that can be downloaded here (9.8 MB).