- "I'm too rich, and too influential to give a flying fuck about what some tux-wearing demon "princess" wants to advertise."
- ―Katie Killjoy, to Charlie
Katie Killjoy is a very tall as well as slim demon. She has short blonde hair, purely white skin, and red eyes with small, yellow pupils. Her most noticeable design traits are her long neck, red lips, big, firm breasts, and wide shoulders. In a shot of the pilot, it is shown that she has a thin waist, along with wide hips. When she moves in a very sudden way, cracking sounds can be heard coming from her body.
In her Full Demon form, she reveals an extra pair of eyes, which, alongside her original pair of eyes, glow bright red. She also summons two extra pairs of arms that resemble the front legs of a praying mantis right below her usual pair of arms.
Katie is arrogant, selfish, and narcissistic. She scoffed Charlie's plan to rehabilitate Demons. Katie cares mostly about her own image, the hottest stories, as well as the latest gossip. She does not care how royal big shot Charlie is, and openly expresses her contempt for her and her ventures. She's also shown to be quite homophobic since she would not even shake hands with Charlie, saying she does not touch the gays because she has standards.
Katie is quite aggressive and seems to always be on edge. She deliberately spills hot coffee on Tom and also insults and threatens Charlie. At the same time, Katie does not tolerate insults in her direction, and when Charlie calls her a bitch, Killjoy instantly falls into a rage and rushes at the princess with her fists.
- Demon Transformation: Killjoy has the ability to transform into a more demonic form when angered.
- Hand-to-Hand Combat: Killjoy is shown to go all out whenever she engages in hand-to-hand combat. Her skills are well known by Trench as he quickly escapes the scene after Charlie angers her.
- Her last name, Killjoy, means "a person who deliberately spoils the enjoyment of others through resentful or overly sober behavior."
- According to Vivienne, she sleeps with a lot of men.
|Hazbin Hotel||Helluva Boss|
|Main characters||Charlie Magne • Vaggie • Angel Dust • Alastor • Husk • Niffty||Blitzo • Millie • Moxxie • Loona|
|Supporting characters||Cherri Bomb • Fat Nuggets • Sir Pentious • The Egg Bois • Razzle and Dazzle • Katie Killjoy • Tom Trench||Stolas • Cletus • Collin • Keenie • Octavia • Robo Fizz • Verosika Mayday • Wally Wackford • Striker|
|Minor Characters||Crymini • Exorcists • Helsa von Eldritch • Lilith Magne • Lucifer Magne • Mimzy • Travis||Barbie Wire • Catfish Monster • Eddie • Joe • Lin • Loo Loo • Loopty Goopty • Lyle Lipton • Martha • Mrs. Mayberry • Ralphie • Sallie May • Stella • Verosika's crew • Vortex|
|Overlords||Alastor • Rosie • Valentino • Velvet • Vox|
|Other Characters||Arackniss • Baxter • "Henroin" • Molly • Seviathan von Eldritch||Fizzarolli • Tilla • Mammon|