Although Cecil no doubt thinks of Slug as “the illustrator for my columns”, my guess is that Slug thinks of Cecil as merely being “my straight man” – i.e. Cecil’s job is to drone on about some obscure topic just long enough to inspire Slug, the real star. And if two oozing kidneys turns out to be funnier/more visually interesting than one liver, then Slug will no doubt follow his muse in that direction.