Thomas and Nellie McElroy are the parents of Chef. Their first appearance was the episode "The Succubus". In this episode, they come to South Park for Chef's wedding. They made a second appearance in the episode "The Biggest Douche in the Universe". Chef takes Cartman and his mother to his parents' manor house in Scotland. They perform a shaman-esque ritual to exorcise Kenny's soul from Cartman's body. Their most recent appearance to date is in "Red Sleigh Down", where they are seen along with Chef in a crowd during the town's Christmas celebration. Interestingly, they are not seen at Chef's funeral in "The Return of Chef."
The McElroys' main subject of conversation is their supposed encounters with the Loch Ness Monster. They repeatedly claim that they have seen him on multiple occasions, and are constantly harassed by him, as he tries to swindle them out of "tree-fiddy" ($3.50). According to Thomas, the monster has pretended to be a Girl Scout, an alien, and Chef's imaginary friend from childhood.