The primary function of a commercial mascot is fairly base: sell product. And yet, a given mascot can take on a life of its own; a life that transcends the merely corporate to become part of the larger culture.
The cartoon cereal mascots are certainly part of that broader cultural heritage. As we grew up, exposed to the antics of Snap, Crackle and Pop, Tony the Tiger, Cap'n Crunch, et al, we find ourselves wondering about the lives the characters lead when they aren't shilling astonishingly anti-nutritious food that's always "part of a balanced breakfast" (by which they mean that it's next to the parts that are actually good for you).
The Breakfast of the Gods web comic offers one interpretation of that. In the story, the characters take on a much more mature role. Count Chochula is an actual vampire, and quite evil. Cap'n Crunch is seen as a wise and benevolent leader who has to make difficult choices. Super Sugar Bear is a creature haunted by the demons of his own addiction.
This isn't to say that the story is without whimsy or, more importantly, respect for its source material. This isn't the kind of story that simply tramples on our childhood memories in order to be edgy and "mature". Rather, the story takes the ideas of the characters at face value and deepens them in order to tell a story that is genuinely engaging and often poignant.