Marvin 'Grandpa' Marsh is Stan Marsh's paternal grandfather and is voiced by Trey Parker, who also provides the voices for both his son, 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' as a result. Despite generally being seen living with his family, Marvin has seldom spoken in episodes in which he is not a prominent character, usually remaining quiet. His presence with the family was maintained, however, with mentions of his extra wheelchair in 'Bloody Mary' and of him being in the bathtub in 'Pandemic'. He also still appeared at family dinners into Season Twelve, after which he disappeared from the home. In 'Cash For Gold', we see he has been moved into Looming Sunset Assisted Living retirement center, explaining his recent absences. (Source: Fandom.com, CC BY-SA)