This started out as a random Mooleskine doodle. The full-spread horizontal lines with wobbles went down on the page, and I sat back to consider what I'd wrought. I believe I thought, "That could be a mouth, but if so a very wide mouth." Aren't you so pleased I'm sharing all this navel gazing with you? Well, as soon as the words "wide" and "mouth" came together, the most natural thing in the world was to tag frog on the end.
In case you're just dying to read the story again, PBS's Zoom has Wide Mouth Frog online.