Here's a cartoonish comet (actually our heros crash-landing) smashing into our client's logo, (funny, we didn't put it that way when we pitched the idea). The ground fog is fake, actually a polygonal object with a semi-tranparent material. Plants growing from the cracks were created using a particle system. Explosion and smoke heavily massaged at compositing stage to create cartoony look.
If you look at the screen shot below, you can see that this particle system is really made up of various balls, each assigned a different level of transparency and a different texture. The sparks are rendered as particles, and the "head" was an animated texture.

Note the forced perspective in the above scenes. The background and surface of the planet were twisted so that it appeared to be taken by a very wide angle lens. SFX done in Prisms 6.5.4

Download a QuickTime of this entire commericial, (15 seconds). Choose .avi files if you're on a PC, and .mov if you're on a Mac. Or go to the Satelight home page and see stills and other Terra-related things.
Click on the image to see
a larger view of this "storyboard."
Copyright© 1996 - 1998, Sean
Lewkiw, Satelight Inc., Wilson Tang, Sapporo Japan.
URL: http://www.lewkiw.com