Sergeant Harrison Yates is the leader of the Park County Police Force and as far as we know, the highest-ranked police officer in Park County. He is usually accompanied by his partner Mitch Murphy or two generic police officers. He first appears as a member of the FBI, but later is seen as part of the Park County Police, a role he has consistently kept in the series' latter half.
Although never being extremely prominent, he has played a major role in many episodes. In "The Jeffersons", when Michael Jackson (also known as Mr. Jefferson) moves into South Park and it is revealed that Yates hates all black men wealthier than himself and frames them — but panics and becomes disillusioned when he realizes that "Mr. Jefferson" is black despite his "white appearance". He discovers Jefferson is indeed black, but when he decides he will give away all of his money, Yates lets him go, having no need to put another poor black man in jail.
In "Cartman's Incredible Gift", when a serial killer strikes South Park, Yates becomes convinced that Cartman has psychic powers that can capture the killer and dismisses proven science such as fingerprinting and blood analysis as "Hocus Pocus". As a result, he arrests and even kills a number of innocent people based on Cartman's alleged "psychic visions", failing to identify the killer as such when he first investigates him, despite an overabundance of evidence.
In "Miss Teacher Bangs a Boy", Kyle reports to Yates and the cops that the Kindergarten teacher, Ms. Stevenson, is in a relationship with his younger brother, Ike. It is shown that Yates and his pals, like all the other men in South Park do not see anything wrong with women committing sex crimes like this one. At one point remarked that he would have gladly hooked up with a sexed-up teacher when he was a kid, again proving to be more of a hindrance than anything else to the case.
In "Butters' Bottom Bitch", he went undercover as a prostitute after learning of an increase in South Park prostitutes. Though it was obvious when he was a man in drag (he retained his male sexual organs, his mustache and his hairy body), no one seemed to notice this or at least chose to ignore it. He also is unaware of the fact he doesn't need to have sex with the Johns to arrest them for soliciting prostitution, something that creeps out the rest of his squad. He seems to take his role so seriously that he not only has sex with his Johns, he also is involved in a bareback gang-bang with dozens of Alpha Tau Omega fraternity men at the college, and he also "falls in love" with his pimp, runs off to Switzerland, is married for a year, before at last arresting him.
In "The Coon", Yates is the primary police officer approached by Cartman in the guise of the Coon. While he seems to see the Coon as an annoyance and tells him to leave, Yates praises the assistance and work of the town's other hero, Mysterion, despite neither hero doing much to assist the police force themselves and the lack of response by them to either hero.
Yates has orange hair, an orange mustache, and thick, orange eyebrows. He wears a white, button-up shirt, black tie, black suspenders, a belt with a gold object at its center, and a brown pistol holder attached to his left suspender. As a prostitute, he wore a short, red skirt, a red bra and a blonde wig.
Yates appears to be rather gullible and believes in the supernatural, and often wastes time by conducting extremely trivial investigations. He seems to enjoy letting other people solve crimes for him, be they supposed psychic mediums, the Hardly Boys, Butters Stotch or Mysterion.
He is married to Maggie Yates, who shares his views on rich black men, as she supported him in "The Jeffersons". Ironically, in "Butters' Bottom Bitch" he engages in a long term affair with a wealthy black man, citing him to be his "pimp".
He has an unnamed son, mentioned in "Cartman's Incredible Gift".
- In "Cartman's Incredible Gift", Yates is called Lou at one point. In the show, he has yet to be referred to by any name since.
- His undercover name was Yolanda in "Butters' Bottom Bitch".
- Like all police officers in South Park, Yates hates wealthy African Americans. However, he seems to have no issue with their race when they are poor.
- In "The Coon", Yates essentially plays the role of Commissioner Gordon to Cartman's super-hero identity, The Coon, and to Kenny's super-hero identity, Mysterion.
- Yates was originally shown working for the FBI in "Christian Rock Hard" and then the South Park Police Department in "Casa Bonita". He was also shown handling a case in Denver in "Free Willzyx".
- His voice is identical to Lieutenant Dawson's from "Lil' Crime Stoppers".
- Yates shoots Michael Deets twice in the face. A detective in "Miss Teacher Bangs a Boy" claims to have shot a man in the face twice, possibly taking credit for Yates' deed.
- Yates has spoken in every season since his introduction in Season Seven.
- As of Season Seventeen, Yates has had a speaking role in 22 episodes.
- "Christian Rock Hard"
- "Casa Bonita"
- "The Jeffersons"
- "Cartman's Incredible Gift"
- "The Death of Eric Cartman"
- "Free Willzyx"
- "Mystery of the Urinal Deuce"
- "Miss Teacher Bangs a Boy"
- "Cartman Sucks"
- "Britney's New Look" (background)
- "Eek, A Penis!"
- "The China Probrem"
- "The Coon"
- "Butters' Bottom Bitch"
- "Medicinal Fried Chicken" (background)
- "It's a Jersey Thing" (background)
- "Royal Pudding"
- "City Sushi"
- "A Nightmare on Face Time"
- "Informative Murder Porn"
- "The Magic Bush"
- "Cock Magic"
Yates appears in the police office as a "friendable" friend. He sends the player to collect five rings from the Nazi zombies. When they player collects the rings, Yates befriends him. Yates cannot be befriended when the Nazi zombies disappear.