A graduate of Princeton University with higher ambitions, Mary McDaniels is the incumbent Mayor of South Park. She is constantly followed by two aides, Ted and Johnson, until Ted's death rescuing the boys from a hoard of Homeless People. She is at times egotistical, thoughtless and a publicity whore, privately mocking her own citizens and willing to do anything to get the problems off her back, hiding behind the "innocent children" or a public debate if possible.
Despite her elitism and thoughtlessness, it is shown she does care about the town to some extent. After seeing in horror the extent of the Hippie Jam Festival she signed off on in "Die Hippie, Die", she attempts suicide by shooting herself in the head. She manages to recover and lives on to make many more bad decisions, including joining the boys' crusade to change the meaning of the word "fag" to mean Harley Riders, and to try to calm the town when it is sued by hundreds of angry celebrities.
She is promiscuous, and has had sex with Jerome "Chef" McElroy, Liane Cartman and Officer Barbrady (multiple times, and in women's lingerie) and has been seeing reading Gazunga's magazine. The Coon suggests she may be a lesbian to the Park County Police in "The Coon". It is notable, however, that she refuses to back down from selling Les Bos to Persians, so her sexuality is likely secret.
- "Kathie Lee Gifford in South Park! Oh my God! This is our chance to make a name for ourselves; to show that we're not just some piss-ant white-bread mountain town." (Weight Gain 4000)
- "Now I'll be stuck in this podunk town forever, with all these stupid hick, redneck, jobless, truck driving idiots." (Weight Gain 4000)
- "All we know right now is that some of our children are camping on that mountain and… Oh, I'm sorry, can I start over? You can edit this right? Ready, 3,2,1 (Melodramatically) All we know right now is that some of our children are up camping on that mountain. " (Volcano)
- "This is an outrage! Get me the Mayor! I know that, smartass, I was being ironic!" (Summer Sucks)
- "So, from this day forward, everyone in South Park will be required to fart on a regular basis to insure that nobody else spontaneously explodes." (Spontaneous Combustion)
- "Mr. Lu Kim, tear down this wall!" (Child Abduction is Not Funny)
- "Mr. Garrison, every Christmas you suggest we get rid of all the Mexicans, and every Christmas we tell you "NO!"" (It's Christmas in Canada)
- "What have I done?" (Die Hippie, Die)
- "You four turdballs in my office NOW!" (The F Word)
- "Oh, that's nice! You made our entire town look like gay-bashing redneck homophobes, but at least you'er sorry!!" (The F Word)
- "Little boy, you don't understand how serious this is! Tom Cruise has put together a class-action lawsuit along with 200 other celebrities!" (200)
- Weight Gain 4000 (s01e02; debut)
- Volcano (s01e03)
- Big Gay Al's Big Gay Boat Ride (s01e04; cameo)
- Death (s01e06; cameo)
- Pinkeye (s01e07)
- Starvin Marvin (s01e09)
- Mr. Hankey, the Christmas Poo (s01e10)
- Mecha-Streisand (s01e12)
- Cartman's Mom is a Dirty Slut (s01e13; cameo)
- Chickenlover (s02e03)
- Conjoined Fetus Lady (s02e05)
- Summer Sucks (s02e08)
- Chef's Chocolate Salty Balls (s02e09)
- Chef Aid (s02e14)
- Cow Days (s02e13)
- Gnomes (s02e17)
- Spontaneous Combustion (s03e02)
- Jackovasaurs (s03e05)
- Chinpoko Mon (s03e10)
- Korn's Groovy Pirate Ghost Mystery (s03e12)
- Mr. Hankey's Christmas Classics (s03e15; cameo)
- Chef Goes Nanners (s04e08)
- A Very Crappy Christmas (s04e17)
- Jared Has Aides (s06e02)
- Child Abduction is Not Funny (s06e11)
- Red Sleigh Down (s06e17)
- It's Christmas in Canada (s07e15)
- Die Hippie, Die (s09e02)
- The Return of Chef (s10e01)
- Cartoon Wars Part I (s10e03)
- D-Yikes! (s11e06)
- Night of the Living Homeless (s11e07)
- Fishsticks (s13e05; cameo)
- The F Word (s13e12)
- Medicinal Fried Chicken (s14e03; cameo)
- 200 (s14e05)
- 201 (s14e06)
- A Scause for Applause (s16e13; cameo)
- In "South Park: The Stick of Truth", a photograph of her and Barack Obama can be seen in her office, implying she may be a member of the Democratic Party.
- In "Death", it is revealed her first name is Mary.
- She has absolutely no dealings with the Japanese Mafia.
Mayor McDaniels is sitting in City Hall and tells the player that the number of Homeless People is making South Park look like an insensitive town and asks them to go beat up all the Homeless People to restore the town's reputation. If the player succeeds, she will grant them a friend request on Facebook. Notably, her aide Ted was killed by Homeless People in "Night of the Living Homeless", so the vendetta may be personal.