I’m interpreting it as kind of making fun of people who help themselves to things. The woman didn’t offer him a cup of coffee, he helped himself to it implying he just felt it was okay. But it wasn’t coffee, so he should have asked before taking. I’m not reading it as a woman playing a joke on him.
Coffee with cream is light colored.
It was funny until Garfield chimed in.
Garfield minus Garfield is always the way to go.
I’m pretty sure that Jon is also below the mice, in the domestic hierarchy. Maybe the spiders, too, though nobody seems to care about them except Garfield.