You play as Stewie and Brian to stop Bertram from building an army to conquer "the" Quahog.
Game play is 3rd person and very linear. There are about 7 or so levels and you can beat them rather quickly, particularly if you're not doing the collecting that's a side quest.
The game is very meh. Almost all the lines are stolen from the show. Ditto for the music. I'm sure they had to get some original dialogue to setup the story, but there wasn't a lot of work done on adding any real humor. If you've seen the shows, you've heard almost all the comedy.
If you grab it for a dollar and love the show, you'll be entertained long enough to beat it if you speed through levels.