If PartiallyClips only ran online, I would not struggle when I write jokes like this. But I did. It was in the last panel, when I was deciding between “Jupiter’s moon, Io” and just “Io.” Just “Io” is funnier, by a noticable amount. But it depends on the reader to know what Io is.
Because the strip runs in newspapers, which get handed out in various venues from bars to coffee shops, I decided that I did not want to risk a lot of readers not getting the reference.
The web audience does not give me these worries. One more small difference between webcomics and print comics, I suppose.