If you listen REAL closely to the tv when T&P are watching you hear...
Mephisto: "The father of Eric Cartman is indeed someone in this room"
(T&P laughing)
Mephisto: "The father is..."
Cartman: "He's my father?"
All they did was use Mephisto's lines from ep 113 and added Cartman's one line...it's another april fools joke...
Now then...that previous post about anagrams could be true...haven't looked at that..