A cartoon is still an unfinished painting.

The most useful definition of cartoon is that it's an intermediate color step in the tempura process. Cartooning is outlining in color on a plaster wall, if you're painting a mural, and you'd have to carve into the plaster with your spatula stick, people use the pointed end and the beveled end to carve figures, form facial features, put folds in the subject's clothes. If you paint directly onto a gessoed canvas, and you'll have to work fast enough to make the paint all chemically cohesive by finishing your artwork before the base coat dries, that's the process of cartooning and finishing a color painting on canvass. Sketches are finished graphite outlines, I know the Speedball ink color cartoons are too, but they're only finished in the sense that your rough draft is for your book, or the alphanumeric outline of your essay is "finished". Sketches and cartoons are finished intermediate stages.

All aliens and UFO glyphy graphicky cliparty things are cartoons.