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Eric Cartman: Despite Cartman’s cruel jabs at Kenny’s poverty, the two have a particularly close relationship (although not as close as Stan and Kyle’s), having been seen playing alone together on several occasions and even claiming to be each other’s “best friend.” While playing together, Cartman often tries to dominant the relationship, bullying Kenny around by making him do excessive work (such as in “Clubhouses”) and trying to control what toys Kenny has in possession (such as in “Cherokee Hair Tampons” and “Chinpokomon”). Because Kenny and Cartman are generally more daring, the two tend to handle mischief better than the other boys, thus leading them into situations alone.
Stan Marsh: While it is not common for Kenny and Stan to spend time together alone, in “The Passion of the Jew,” the two are shown interacting and going on a separate adventure after seeing Mel Gibson’s The Passion of the Christ. They generally get along very well, and Stan has been shown to worry about the exact depth of his relationship with Kenny, most notably in “Kenny Dies,” where he’s concerned about just how much a friend he is to Kenny. Even when Cartman and Kyle come to terms with Kenny’s terminal illness, it is Stan who has the most trouble accepting the boy’s death.
Kyle Broflovski: Kenny’s relationship with Kyle is similar to his one with Stan, being that two rarely spend time alone together, albeit a few exceptions. In “Jewbilee,” Kenny suggests they watch the meteor shower together, leading to the two attending Kyle’s Jew Scouts meeting. In the episode, Kyle helps Kenny pass as a practicing Jew, but later, when Kenny is discovered not to be Jewish, Kyle betrays him by lying to the Scout Leader by claiming Kenny told him he was, in fact, a Jew. Despite this betrayal, Kenny willingly dies in order to save Kyle’s life (along with the other Jew Scouts). In “Kenny Dies,” Kyle shows the extent of his dismay for Kenny’s illness by crying in Cartman’s arms, and in “Major Boobage,” Kyle is the first to recognize Kenny’s “cheesing” problem.
Butters Stotch: While virtually having an extremely limited interaction, Butters and Kenny are still known to get along fairly well. In “Fat Camp,” Butters lets Kenny borrow his R. Kelly thermos, and later, in “Major Boobage,” Butters shows concern for Kenny’s “cheesing” addiction, where he attempts to help the boy break his drug habit and even showing individual concern for Kenny’s health. Besides these two key instances, Butters and Kenny have never had screen time alone together. It is worth noting, however, that in “Good Times with Weapons,” Kenny accidentally threw a ninja star into Butters' eye, although the boy showed little remorse for his actions.