Reality to PC Principal. Both are straw characters whose M.O. involves harassing others; except while PC P sees himself as a protector of the underprivileged who never listens, Reality sees himself as the smartest guy in the room who refuses to be silenced. Both also contributed to Butters' Sanity Slippage, yet in their minds they were trying to help. Reality is killed off after one episode for calling everyone out while PC P is kept around for the long run so that certain people can feel good about themselves.
In season 21, there is a couples version of it. Cartman and Heidi are toxic to each other, Cartman is selfish and manipulative, decrying he might kill himself whenever Heidi tries to get away, and because of him, their relationship keeps getting worse, it's also shown that, for the majority of the time they're together, they do not enjoy each other's company. Tweek and Craig are a couple that also has a hard time understanding each other sometimes, but they do make efforts to it, and end up making up and moving on, they never threaten to break up and spend a considerable amount of time enjoying each other's company.
Butters' personality highlights Cartman's by contrast, as both are naive, ignorant, and seek attention, but differ from each other in that Cartman is a complete Jerkass with no moral decency whatsoever and Butters is a sweet and endearing All-Loving Hero without a single mean bone in his body.
Randy to Stan, the sanest kid, has the craziest parent. Their interactions highlight how much more mature Stan is to his Manchild father, and how Stan serves as the Only Sane Man.
Randy to his Closer to Earth wife Sharon. Sharon is generally far more levelheaded and less impulsive than her husband, with a much more restrained wild side. Increasingly, she becomes the only real adult in the house, with Randy devolving more and more into a man-child.
Henrietta for Call Girl in terms of being the only female buddies in the game who happened to be dragged into the boys' superhero LARP. Aside from that however, the two couldn't possibly be any more different. Call Girl wears shades of purple and pink reflecting her perky and bright personality, while Henrietta wears black reflecting her cynical and dark personality. Call Girl has a secret identity that she goes through lengths to hide (Wendy), while Henrietta doesn't even bother coming up with a superhero persona. Call Girl willingly offers her assistance to The New Kid and their friends, while Mysterion must ask Henrietta to help him and his allies. Call Girl's powers are based on modern technology and dealing heavy damage to multiple enemies, while Henrietta's powers are based on the occult and supporting her allies. In terms of religion, Call Girl is an atheist while Henrietta is a satanist.
Henrietta is also one to her Annoying Younger Brother Mintberry Crunch in terms of being exclusive DLC allies. Mintberry Crunch Crunch is much more childish and upbeat in contrast to Henrietta's cynical and dark personality. Mintberry Crunch willingly offers his assistance to the New Kid and their friends in the DLC Sidequest "Bring the Crunch", while Mysterion must ask Henrietta to help him and his allies in the DLC Sidequest "From Dusk Till Casa Bonita". They also don't seem to get along most of the time whenthey're both in the same team roster.
Kyle and Cartman have developed to be each other's foil, due to their intense rivalry showcasing their polar opposite moral beliefs. Both are very stubborn and hot-headed at times, but Kyle is very empathetic and strives to do the right thing, while Cartman doesn't care about anybody but himself and always takes the most selfish and often bigoted approach. A few episodes, particularly "Crack Baby Athletic Association," show that Kyle isn't above Cartman's level of moral dubiousness if Cartman can manipulate Kyle into believing that he's doing the right thing.
Stan and Cartman's future selves during the Post Covid two-parter. In the first part, Stan, despite being the Only Sane Man and a relatively Nice Guy in his childhood, grew up to be lonely, miserable and an alcoholic, while Cartman (one of the biggest Jerkasses in all of animation) grew up to be a successful family man with a loving wife and children. At the end of the second part, after the past is changed, Stan is the successful one and Cartman is the lonely miserable alcoholic. Compounding it further, Stan doesn't have kids of his own, but he's an Honorary Uncle to Kyle's children and is in an implicit relationship with Wendy, while Cartman has nobody. Stan is a well-respected astronaut while Cartman did nothing with his life. Finally, even at his lowest, Stan still had a job and a roof over his head, as well as a wife in the form of an Amazon Alexa (which is nowhere near the real thing, but it's better than nothing). Cartman is a filthy hobo who has driven everyone away from him, spends all his time cursing at people on the street and has nothing going for him.
