Detective Jarvis appears in the Season Ten episode, "The Return of Chef". He comes to South Park Elementary to talk to the children about Chef's recent pedophilic behavior, which was later revealed to have been brainwashing from the Super Adventure Club. He says he wants to collect testimony from the children, but only shows how a pedophile would treat them.
He has brown hair, which he combs back, and wears a black suit with a dark red tie and a yellow badge.
He seems to take his demonstrations very seriously, demonstrating the actions of pedophiles with unusual enthusiasm. He also seems very childish when convinced of something, as shown from his responses to Stan Marsh refusing that Chef is a pedophile.
There is another character with the surname name Jarvis, it is unknown if they are related.