If you cheat in South Park: The Fractured but Whole, Cartman will show up to yell at you, like a far fouler version of Nintendo's Mr. Resetti digging up out of the ground to chastise you for changing the date in Animal Crossing.
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Of course, the definition of "cheating" is a bit murky in the context of a single-player RPG. In this case it means finding a ahead of where you're actually supposed to discover it in-game, whether by looking it up or bringing back knowledge from a previous playthrough. Certainly, you could never guess that Cartman would lock his hidden basement base behind a like "Fuck You Mom." That one's impossible to crack.
If you put in the before encountering the code in-game, Cartman shows up in the guise of New England Patriots coach Bill Belichick and says "Hey, Tom Brady. You wanna play the game or do you just wanna be known as a smug cheating bitch for the rest of your life?" That's a hot American football reference for all of you.
The clip above comes courtesy of Kotaku, and it seems the Easter egg has a follow-up during a later sequence at the church.
Fractured but Whole released just yesterday, and we've found it to have a definitively South Park.