OK, so here is my Watsonian question: Does Arthur have a tongue?
I believe he doesn't, because there is no visual distinction between his "tongue" and the other facial features of Pintsize, Punchbot, O'Malley... or heck, of *any* of the other AI's. Correct me if I'm wrong, but I don't believe we've ever seen any interior features of an AI's mouth, so we don't know whether they
have interiors. As far as we know, there's nothing but a highly malleable colored surface layer over a white sub-layer that keeps foreign objects* and dust and grit out.
In
strip 3304, May realized "I could fill my mouth with lube and let a dude go to town." So presumably at least that model has a space inside the head into which the inner layer could stretch.
Anyway, I think the "tongue" is no different than the eyes and mouths we've seen all along: a gap caused by stretching of the outer colored layer to expose the inner white layer.
I find this question fascinating because it speaks to the level of visual shorthand we comics readers have internalized. I've spent decades reading comic books and comics, so I've got all this wetware that extrudes visual elements such as mouths and tongues from simple two-dimensional shapes. I see stuff that's not there in the panels, and every once in a while I step back and realized that people who don't have that wetware must not have the slightest clue how anyone could, say, be moved to tears by a web comic about an ex-military AI in a gynoid battle droid body falling in love with a human woman.
In short, we've got a robust semiotics suite, and the implications are fascinating. For instance, two people on the Patreon forum asserted that that feature we see on Arthur's face is a tongue, though I believe they have no justification for this. But neither do I have any justification for my assertion. It speaks to the interplay between artist and audience, and I can't help but think that at least some of it is intentional on the part of the artist. I mean, Jeph's representation of human faces has changed radically over the years, but Pintsize's face has stayed more or less the same, so it's not unreasonable to ask—perhaps even from a Doylist perspective—whether Arthur has a tongue.
*Oh nuts. As I was writing this, I remembered that Punchbot swallowed his car keys, so that sort of throws my theory out the window.
Drat. I mean, "brutal self-own, ell em ay oh."