Toonboom.
Well-- more specifically
2D Puppets. While Toonboom wasn't the pioneer of 2D puppeteer-ing, it definitely made it immensely easier and it's the industry standard. New episodes of lazy cartoons have hardly any new artistic content in them. At the most maybe a couple of new backgrounds, props and two different faces.
Say what you want about The Simpsons but the old animation style vs the new one is really the perfect example of why a lot of cartoons seem less-- well,
animated. This side-by-side really says it all.
Sure the new stuff is clean but man it's
so freakin stiff.
That isn't to say that all cartoons with 2D puppets are lazy though.
Some shows actually utilize this stuff pretty well and are able to keep their cartoons fresh-- but a lot of shows don't. Especially super young kid shows.
This makes having young relatives a nightmare because when you see them you have to sit though shit like this:
http://pbskids.org/wildkratts/
/:autism: