You haven't watched the whole series? Oh man... It's a completely different show after season four.
And watch seasons one and two with the commentary track on. It's (a) funnier than the show and (b) incredibly addictive. Basically, they spent the first two seasons drunk and insane all the time.
Then they got big and did that minor reboot in season three. And then they just wheeled off into great times. Seasons four, five, and six are astounding. Season seven is where they started to fall, and season eight is horrific (though more watchable than the first two).