Marvin Marsh

Marvin "Grandpa" Marsh is Stan Marsh and Shelley Marsh’s paternal grandfather and is voiced by Trey Parker, who also provides the voices for both his son, Randy Marsh, and his grandson. He is a member of the Hare Club for Men and tries to persuade Stan to kill him on a regular basis. He made his first appearance in the Season One episode, "Death".

He has dementia, which is characterized primarily by memory loss and refers to Stan as "Billy" and Shelley as “Sally” as a result.