This series revolves around a twelve-year old goth girl named Riley Killian and her pet bat, Pain, as they deal with various problems whether it's about the supernatural or her home/school life.
- Riley Killian (voiced by Grey Griffin) - a 12-year old goth girl who is usually angry and is shown to act cruel towards others, including her family (except Pain). However, despite her rude attitude, she does care for her family, she just doesn't like showing it.
- Pain the Bat (vocal effects by Frank Welker) - a bat who is Riley's pet and is loyal to her. He is the only character in the series that Riley shows sympathy to without a problem.
- Ross Killian (voiced by David Kaufman) - Riley's 15-year old brother who enjoys playing video games and is usually a jerk to Riley.
- Hannah Killian (voiced by Mae Whitman) - Riley's 6-year old sister who, unlike Riley and Ross, is a nice girl rather than a jerk. She can also be sensitive.
- Natalie (voiced by Colleen Villard) - a kind girl who always does her work and is considered to be Mrs. Swellsman's favorite student along with Edwin.
- Edwin (voiced by Carlos Alazraqui) - an intelligent boy who does very well in Mrs. Swellsman's and does his work on time. Because of this, he is best friends with Natalie.
- Oscar (voiced by Benjamin Diskin) - an overweight boy who hates school and would rather play video games and eat food than do schoolwork.
- Arianna (voiced by Ashly Burch) - a spoiled girl who is always seen wearing make-up, claiming she is the most beautiful girl in the school.
- Zeke (voiced by Phil LaMarr) - an African-American boy who wants to be a rapper just like his idol, Witty Will, but dislikes school.
- Issac (voiced by James Arnold Taylor) - an idiotic boy who is considered an annoyance to his classmates.
- Mrs. Swellsman (voiced by Susanne Blakeslee) - a middle-aged woman who is Riley's teacher.
- Mr. and Mrs. Killian (voiced by Corey Burton and Kath Soucie, respectively) - Riley's parents.
- Grandma Killian (voiced by Candi Milo) - Riley's grandmother who, like Riley, is into the supernatural.
- The Hand Man (voiced by Jim Meskimen) - a hand-like creature Riley summoned who shows respect towards Riley.
- Austin Miller (voiced by Yuri Lowenthal) - a 12-year old goth boy who Riley had a crush on and, unlike her, is rather friendly and calm.
- Julie Wright (voiced by Ashley Johnson) - a 15-year old gamer girl who Ross first found while playing Union of the Mythical online, with her considering him annoying at first until they realized they had several stuff in common and eventually decide to stick together. She is later revealed to be Austin's cousin as Riley befriended her after finding out about that.
- Penjamin (voiced by TBD) - a fictional cartoon pig from an education show called Learn About Life with Penjamin, as he teaches kids about life.
- Destiny the Face Paint (voiced by Kari Wahlgren) - a Face Paint whose family moved to Happsburg. When she encountered Riley, she tries to make friends with her, but due to her immaturity, she ends up causing trouble for her, causing Riley to not be friends with her due to finding her annoying.
- The Stone Imp (also voiced by Jim Meskimen) - an imp made out of stone who likes to hang out around places.
- The Eye Serpent (voiced by Billy West) - a serpent with an eyeball as its head who has the ability to hypnotize others.
- The Gingerhill Triplets, consisting of:
- Lara (voiced by TBD) - TBD
- The Dark Girl (voiced by Erica Lindbeck) - TBD
- Jessie Criss (voiced by Stephanie Sheh) - a shy teenage girl who prefers to say home and read a good book, yet is pushed around by others, especially Ross.
- The Cuddly Monster (voiced by Rob Paulsen) - a pink monster who was accidentally summoned by Riley and was rejected shortly after, and because of that, he holds a grudge against her.
- Mrs. Cuddly (voiced by Courtenay Taylor) - a pink monster created by the Cuddly Monster himself who eventually becomes his wife.
- Veronica "Vala" Verminee (voiced by Tara Strong) - a 12-year old blonde girl who enjoys bullying other people, especially Riley.
- Becca Perez (voiced by Kimberly Brooks) - a 12-year old Latino girl who is Vala's best friend, and like her, she enjoys bullying Riley.
- Clay the Clown (also voiced by Rob Paulsen) - a clown who is completely insane.
- Dr. Vermïn (voiced by Gilbert Gottfried) - a dentist who is revealed to not be human.
- Sadie (voiced by Cristina Pucelli) - a seemingly normal 11-year old girl who is revealed to be a deranged humanoid creature created by the Cuddly Monster.
- Patricia (voiced by Erica Lindbeck) - an arrogant 20-year old woman who was the Killian children's babysitter.
- Martha the Mind Taker Queen (voiced by Laura Bailey) - a Mind Taker who decided to take over Happsburg, causing massive chaos.
- Kate (voiced by Cathy Cavadini) - a Mind Taker who is Kate's second-in-command.
- Vladikoff Dracul (voiced by Greg Ellis) - a vampire who attempted to turn whoever he sees as the "chosen one" into a vampire and take over Happsburg.
- The Happsburg Slasher (voiced by Liam O'Brien) - a serial killer who uses a garden hoe to attack his victims.
- The Locker Ghoul (voiced by "Weird Al" Yankovic) - a ghoul who lurks into random lockers whenever the school it enters is closed.
- Duck E. Candy (voiced by Gregg Berger) - an animatronic duck that Cuddly Monster hijacked to get revenge on Riley.
- Lana (voiced by Jessica DiCicco) - a snake-like creature who tried to eat Ross.
- The Torthons Family, consisting of:
- Mr. and Mrs. Torthon (voiced by Jim Ward and Jill Talley, respectively) - a grumpy couple who often bicker with other couples.
- Isabella Torthon (voiced by Danica McKellar) - a selfish teenage girl who only cares about herself and being popular.
- Isaiah Torthon (voiced by Jason Marsden) - a troublemaking tween boy who likes to ruin other people's stuff just for the fun of it.
- Simon Torthon (also voiced by Kari Wahlgren) - a bratty little boy who will throw temper tantrums if he doesn't get his way.
- Froke (voiced by John DiMaggio) - a frog monster that the Cuddly Monster teamed up with to make frog zombies.
- The Book Worm (vocal effects by John DiMaggio) - a worm creature the Cuddly Monster created that once tried to eat Riley's book.
- The Ghost of the Happsburg Battlefield (voiced by Clancy Brown) - a ghost of a soldier whose mind is filled with wrath due to losing everything he had during a war and was responsible for locking Riley, Oscar, Zeke, and Issac in the cabin.
- Little Riley (also voiced by Kari Wahlgren) - a demon that can turn into a doll version of anyone the person who summons them prefers them to be. After having enough of Hannah annoying her, she decides to cause chaos to torment Hannah.
- Little Pain (vocal effects by Frank Welker) - another demon who can turn into a doll version of anyone the person who summons them prefers and is Little Riley's pet.
- Mary and Gary Sue (voiced by Kari Wahlgren and Daran Norris, respectively) - a creepy couple of siblings who manipulates people to be "perfect".
- Valerine Viper (also voiced by Jessica DiCicco) - a teenage girl who has been known for tormenting students in her high school, including Ross, as Riley sees her as wannabe of her.
- Kim and Kimmy (voiced by Cristina Pucelli) - a ventriloquist and her dummy who are sorta creepy.
- Energan (voiced by Troy Baker) - a powerful energy-like monster who feeds on energy from other living organisms so he can be stronger.
- Raven the Wicked (voiced by Christian Borle) - a wicked, manipulative, and cruel sorcerer who can control dark magic and turn into a flock of ravens.
- Chet Cheyetson (voiced by Andrew Rannells) - a famous talk show host of The Chet Cheyetson Show! who is rather creepy.
- Junk Demons (vocal effects by Jim Meskimen) - a bunch of terrifying monsters made out of various junk parts.
- The Shadow Cult (voiced by TBD, TBD, and TBD, respectively) - a villainous cult who is obsessed with summoning a shadow creature and is willing to do anything to free the monster.
- The Runaway (voiced by TBD) - a spirit of a teenage girl who ran away from her family and now whisks away runaways like her into a creepy pocket dimension.
- Shadow Emperor (voiced by Jess Harnell) - an egotistical short imp who runs an empire consisting of evil imps like himself and wants to invade Happsburg.
- Terror Turtle (voiced by TBD) - an evil turtle who causes chaos and wants to cause fear into people.
- The Personrileys, four versions of Riley who all represent the negative emotions inside of her. Consisting of:
The animation for the series is outsourced to Rough Draft Studios in Seoul, South Korea.
The series received generally positive reviews from critics and fans alike, being praised for its dark humor, animation, TBD.
Potential CBS All Access film
Comic book series
See Theme Song.
- This is the second Nicktoon to be rated TV-PG, with the first one being ROBLOX: The Series.
- In The Dimension, a broken version of Goddard from The Adventures of Jimmy Neutron: Boy Genius can be seen.
- In Curse of the Lonely Tree, when a minor character was reading a newspaper, a picture of Plankton from SpongeBob SquarePants can be seen under the headline, "New Species of Zooplankton Discovered?!".
- In the same episode, we see a kid on a missing poster who resembles Clyde McBride from The Loud House.
- In TBD, Hannah was seen humming the royal anthem of the Kilted Yaksmen from The Ren and Stimpy Show.