Mel featured in an earlier episode of the Simpsons where with Homer's help he shot a re-make of "Mr Smith Goes To Washington" complete with Congressional blood bath ending. But his variance from Roman Catholic doctrine make me think of Homer's flirtation with the Faith:

"Once you go Vatican, you can't go back again!"

from the episode where Homer and Bart consider Catholicism:
The Father the Son and the Holy Guest Star

Homer (after finishing confession): Woo-hoo, I'm clean! In your face, Lord!
Sean: Not yet, Mr. Simpson. I can only absolve you if you're a Catholic.
Homer: Uh-huh. And how do I join? Do I wail on some Unitarians?
Sean: Well, it's a little harder than that. It starts with looking deep inside yourself. (Homer groans) But it ends with bread and wine.
Homer: Woo-hoo!

Near the end Bart gives the message:

Bart: Don't you get it? It's all Christianity, people! The little, stupid differences are nothing next to the big stupid similarities!