They made a second appearance in the Season Six 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. Although they are successful in exorcising Kenny's soul, they are unable to re-seal it because Chef hadn't brought a victim child to sacrifice. Instead, Kenny finds his way into a pot roast Nelle was preparing, much to her dismay.
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. They are not seen at Chef's funeral in "The Return of Chef.", making it believed that they died before their son did.
They both appear to be very old, with wrinkles and white hair. Thomas is balding and wears a blue suit and black tie with an orange shirt. He occasionally dons a pair of reading glasses.
Nelle has a full head of curly white hair and wears a yellow dress and a pearl necklace. Her eyes seem to be perpetually closed. She also appears to carry a small blue handbag around. In "The Biggest Douche in the Universe", she appears in full voodoo regalia, with a long white robe, an intricate mask and headdress, fake wings and one scepter in each hand.
They both appear to be friendly folk, being very accommodating to Liane Cartman and Eric Cartman when they visit their house in "The Biggest Douche in the Universe". Nelle appears to be a little senile and over-concerned with household duties, worrying about Kenny's spirit getting all over the curtains and her pot roast, and occasionally muttering things to herself.
The McElroys' main subject of conversation are 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.
They appear to have a good relationship with their son, Chef, whom Thomas refers to as "Junior". Because he lives in America, they appear to miss him a lot, since as he appears at their doorstep in Scotland they appear overjoyed to see him again in "The Biggest Douche in the Universe".
- "The Succubus" - Come down to South Park for Chef's wedding.
- "The Biggest Douche in the Universe" - Chef brings Cartman and his mom to see his parents to help them exorcise Kenny McCormick's spirit from Cartman's body.
- "Red Sleigh Down" - Seen in the crowd with Chef during the Christmas celebrations.