I'm editing the original strip to reflect the correct usage of "homophones", with a doff of the cap to my various professors who e-mailed me. (It's like I'm back in grad school! They keep pulling me back in!)
Here's where my mind went astray. For some reason, I thought that "homonym" was the umbrella or catch-all term encapsulating both homophones and homographs. The Greek suffix "-nym" being "name" I *thought* put it as a classification encapsulating "-phone" ("sound") and "-graph" ("writing"). But alas, my supposition would earn me no supper tonight. Turns out I'm just a moron.
So! To my former professors, a kind thank you...and you shall get no more language classification jokes from me for a while. :)