|South Park character|
|Birthday||September 1, 2029|
|Voiced by||Trey Parker|
|First||Welcome to the Future|
|Last||Welcome to the Future|
Billy Marsh resembles Stan alot in many ways. He is named after the name that Marvin Marsh used to call Stan in "Death". He wears a brown shirt and blue jean, similar color of apparel that Stan wears. He is friends with Dylan Broflovski, Andy Stotch, Adolf Cartman, and Tommy McCormick.
- Even though he is said that he is the future son of Stan and Wendy, the future always changes and it is possible that he won't be born along with his friends.
- In the episode, "Death", Grampa Marsh mistook Stan's name to be Billy, which is where Billy's name comes from.