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.
- 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 Eye Serpent (voiced by Billy West) - a serpent with an eyeball as its head who has the ability to hypnotize others.
- 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) - TBD
- 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 TBD into a vampire and TBD.
- 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.
- Emma C. Mongoose (voiced by Wanda Sykes) - an animatronic mongoose who is Duck's girlfriend.
- Cody T. Cobra (voiced by TBD) - an animatronic Cobra who is Duck's best friend.
- Charlie the Brown Gremlin (voiced by TBD) - an animatronic brown gremlin.
- Lana (voiced by Jessica DiCicco) - a snake-like creature who tried to eat Ross.
- The Torthons Family, consisting of:
- 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.
The animation for the series is outsourced to Rough Draft Studios in Seoul, South Korea.
(reserved for Green)
Potential CBS All Access film
Comic book series
- 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.