From "Aesop's Fables" -- The lion and the ox. (1968)
One of the qualities I find magnetic about Syverson (and many others) is the spontaneous feel of his art. The more you could add to these drawings, the more they might lose. I think that's one of the things I enjoyed most about the "xerox era" of hand-drawn animation: the drawings could be loose enough to still show erasures and not even have to be "closed off" (in the digital era, this became basically impossible). Those little gaps of freedom in the lines still make me smile. Probably because I am prone to draw that way myself all the time. I have always found it very tedious to close off every area of a drawing, and can't do it reliably well without stiffening things up.
The other quality Syverson's work typifies for me is simplicity. Simplicity is one of the most difficult things to achieve and has as much to do with knowing what to leave out entirely (and what to merely imply) as it has to do with what to leave in.
One of my favorite quotes ever:
"Everything should be made as simple as possible, but not one bit simpler." - A. Einstein