I'm starting with the first webcomic I ever read. (Not this one in particular, but Dinosaur Comics in general. This is just an example of one I like.)
And the Pokemon with which I feels it corresponds is:
Ubiquitous but undeniably cute. Brilliant in its simplicity. You would have a hard time finding someone on the internet who did not at last have a basic knowledge of who Pikachu is, just as you would have a hard time finding someone on the internet who had not at least heard of Dinosaur Comics.