The show is based off illustrated books by Brian Wood.
https://books.google.com/books/about/The_Cramp_Twins.html?id=EVr8JwAACAAJ&redir_esc=y&hl=en
The book's art style is a lot different from that of the animated series and this show Doug which I've never heard of and I specifically looked up to see that its completely different.
The lines when I first saw the show I thought they were shivering or vibrating, but when you get used to it you don't pay attention to it. In fact they actually all shiver and vibrate in Ed, Edd and Eddy, which is way more obvious and distracting.
In fact there are hypotheses going around that the characters' skin color is because they've been exposed to toxins from Soap City. As a matter of fact the more I look into this show, the more it shows a darker and sinister side where characters are physically and mentally affected by the place they live at and the more down to earth are the Swamp Folk.
I really liked this show when I first saw it around 2003 - it struck me as weird and uncanny and I really liked it. It's OK if you don't, but it's not a bad show, just the plot sometimes feels a bit dodgy, but if you look under the surface, you can picture a whole different and weird story that kind of resembles Eerie, Indiana.
If you want to watch it online, you can do so here:
http://www.toonova.net/the-cramp-twins
and here:
https://kisscartoon.io/Cartoon/The-Cramp-Twins/