Mynarski Forest Official Vintage Archive
Besides the punchline at Heywood's expense, there's actually quite a lot going on under the surface of this one little strip.
In a lot of web comics, interspecies physical relationships tend to happen at the drop of a hat, but that's just not the way things work in real life. Even amongst the same species, individuals tend to gravitate towards similar individuals; and while human couples can and do cross cultural, racial, and class barriers, even today it's not the norm, and such pairings confront all sorts of challenges and obstacles. From the very begining I felt Skippy and Liska's relationship should face such difficulties, both from the need of plausible suspension of disbelief and the humorous possibilities such difficulties inherently provide.
We also see in this strip that Liska actually does care what Skippy thinks about her and feels more than a little insecure about it, that there's more depth and vulnerability to her character than her wild, apparently sociopathic behaviour suggests. And that Skippy has insecurities of his own that make him uncomfortable about exploring and confronting the issues himself.