Ok, I don't pretend to be an artist like Bil Keane pretends to be, but I can probably guess how a normal drawing would be done. If you're drawing a mom with a bunch of kids crawling all over her, I think it's reasonable that you'd draw the mom first, then draw the kids.
So, at some point, Bil Keane was looking at something like this:
1. Do you think this was an accident that was punctuated with a suprised "well...hell-LO there, Mommy"?
2. Did he stop at this phase of the drawing? For maybe 8-10 minutes?
3. Do you think he did a "save as..." at this point and saved it to My Documents\Old Bills\Misc\1983\September\Lawn and Garden\October\Misc\Wheelbarrow.jpg?
4. When you remove all of the kids, Barfy looks way more inappropriate, but makes way more sense. Especially if he's the one talking.