It was clear as soon as I saw this clip that the woman in the wheelchair had to have the punch, had to steal the show.  I thought about some ways to work it so that she could just sit there stealthily until delivering a knockout in the last panel, like she was a vegetable or completely demented or something, but they didn’t lead to anything worthwhile.  Instead I just gave her the upper hand throughout, implying a little dementia on the order of crazy-like-a-fox.

As far as what’s actually happening in this little storyline, I don’t know.  That’s part of what makes it funny, I think.  I was just reading an article in Scientific American where they were giving people MRIs while they watched the Simpsons.  It noted that surprise, incongruity and ambiguity were all key elements in humor.  Surprise and incongruity I have thought a lot about, but I hadn’t much considered the role of ambiguity in gags until now.