Have you ever seen
BLOGregard Q. Kazoo? It's the Foster's blog Craig started back in '06. He deleted a good chunk of the latest entries (it went up until like May of '07 or something like that), but he kept the earliest posts up, and there's still a lot of fascinating info there.
They both had a big hand in pretty much every corner of the show. And yup, Craig was the head of it all. He even voiced his own character for a few seconds in "One False Movie". Lauren did a lot of character design, too. Both working on what they looked like and what their personalities would be.