See, the thing of it is, even a majority of their original work is derived from pop culture in same way or another... matter of fact, you mentioned "Eight Balls of Fur" as an original, when in actuality, it too is a parody of the old Jerry Lee Lewis hit "Great Balls of Fire".
That's not to say all of their original work is inspired or influenced by pop culture, but some of it is.
That's not to say all of their original work is inspired or influenced by pop culture, but some of it is.