It's so obscure it's practically an inside joke. Yet it makes you want to watch every episode again, scene by scene, on your own, with your hand hovering over the pause button just in case you've missed some bonkers reference you'll then have to google because you wouldn't get it anyway.
As for my opinion of S4, I was horrified by the first episode, and worrisome for the first 4 or so, but retrospectively delighted by the end. It was, in hindsight, a wonderfully bold way of writing and presenting a comedy. Even though there were a few weak eps, it was worth it alone for Gob's plot line and the Catch a Predator sequence in episode 5, every line of which after he walks into the house is absolute AD Tobias gold.
And as it is such, so also as such is it unto you.
"Oh, I thought you were hair"