The first one here shows a couple subtle shifts and tweaks made to the concept before sending it off to the newspaper. Cutting in a few areas for shading provides the crucial contrast for enhanced depth and dimension.
Another key factor is compositional arrangements of the core visual elements.
Another one with not so much evidence of editing but be assured it possibilities pile up nevertheless just off-paper and inside the cartoonist's head (a key indication of this mental activity would be mistaken for a blank staring off into space).
Cribbing from Wikipedia is common enough that next time the annual drive for donations comes around I really gotta tip them, especially how much I use it for hyperlinks here. Update: Or not.