I'm going to guess that you'll be able to identify most of them (if not all of them---depending on your familiarity with the characters). You should notice right off the bat which one's pop out the most to you. Some are recognizable, but have much more complicated shapes. Notice the variety! Especially in the somewhat limited cartoon genre.
Notice the pairs of characters I've included. If you're designing a duo---design them together. See how the negative space around the pose is crucial to making them look active and dynamic—how each character fits into the other.
Here's the take away. When you're designing a character, pay attention to the form...think about positive and negative space, and how it would translate to a silhouette. The language of cartooning lends itself to this so well, which is why so many characters become icons. It might be fun to do a quick line-up of some of our FableVision characters, to see how they stand up to the silhouette test.
Hope this was fun! Let me know your thoughts :)
UPDATE (6-23-08) I just found a great post over at Aviary by Meowza who offers a great analysis on the importance of silhouette and foundation in character design. Definitely go check it out!