Matt Groening's Drawing Style

Im a fan of the simpsons and futurama and wont usually compare them but I have been trying to copy his style on my computer and trying to draw friends and family in simpsons style, It was alot easier than I though, because Im a big fat idiot when it comes to art or cartooning so I assummed I would fail. Anyway, what im saying is, despite the fact that the humans in Futurama are not yellow, and are slightly differently drawn there must be some sorta of continuety...Ive noticed that there the facial expressions seem to goovern 90% of each face yet every cahractor manages to still look them no matter what pose, thats the bit I find hardest, anyway, im jibbering.