- Affectionate Gesture to the Head: In "Vote for Casper" Mantha strokes Casper's head when she reveals that she did in fact vote for him. In "What Possessed You?" Stretch also strokes Casper on the head when he believes Casper gave up on being friendly.
- Anti-Hero: At first and for most of the series, he is unambiguously friendly and kind, even if he is more than a bit snarky who isn't above lying and generally being an occasional "trouble-maker" in school, even during the earlier installments. Then Casper got Darker and Edgier, doing things that become much more questionable as time goes on, even when they're being used to reach goals that are unquestionably heroic.
- Beware the Nice Ones: Pushing him around too much is not a good idea and if you threaten his friends, his anger gets epic.
- Brilliant, but Lazy: He is great at scaring people, both on purpose or in accident, and even scarred a crowd better than Kibosh himself once and he wasn't even trying to.
- Character Development: In season 2, he's gotten a lot more aggressive towards Thatch and will fight back when Thatch picks on him.
- The Chosen One: Fans believe that Kibosh wants to make Casper the next leader of the Underworld.
- Innocent Blue Eyes: Blue eyes and a sweet personality, plus he's the hero of this story.
- Nice Job Breaking It, Hero!: His friendliness often causes problems for both his fellow creatures and himself.
- Older Than They Look: He appears to be somewhere around Jimmy's age, but he is really more than two hundred years old.
- Out-of-Character Moment: In "Potent Brew" Casper is trying to pull something from a toddler's grip and when Mantha scares the toddler into letting go, making her cry, Casper thanks her.
- Sensitive Guy and Manly Man: Sensitive Guy to Ra's Manly Man. Ra is more extroverted than him, while Casper is more calm and feminine.
- Teacher's Pet: Kibosh clearly favors him.
- Why Couldn't You Be Different?: The Ghostly Trio wants Casper to be scary and a prankster like them.
An Egyptian prince.
- Attention Whore: His obsession with getting attention does sometimes get him in trouble, though.
- Distressed Dude: One notable example would be "Dimension Demended", where he gets stuck in the Dimension Tube.
- Older Sidekick: Ra is 2500-years-old while Casper is hundreds of years old.
- Older Than They Look: He appears to be somewhere around Jimmy's age, but he is really almost three thousand years old.
- Sensitive Guy and Manly Man: Manly Man to Casper's Sensitive Guy. Ra is hot-blooded and manly, while Casper is calmer and more effeminate.
Casper's other best creature friend and love interest who is a "Zombie Activist".
- Berserk Button: DON'T talk trash about zombies, some actors found this out the harsh way.
- The Determinator: Takes a lot to get her to give up.
- Friendly Zombie: This young zombie girl has a loving zombie family. She's one of Casper's best friends and is generally a Nice Girl.
- Interspecies Romance: Interspecies paranormal romance. She has a crush on Casper. She's a zombie and he's a ghost.
- Our Zombies Are Different: She is actually smart and agile. The walking slowly while chanting "Braaains..." routine is just a scare tactic zombies use. And though she does eat brains, it's not all she eats.
- Pink Means Feminine: Subverted. She wears a pink shirt and her shoes have pink shoelaces but she's rather tomboyish.
- The Smart Girl: She's clearly one of the smartest characters in school, thus subverting the stereotype that zombies are mindless.
- The Smurfette Principle: She's the only female in her group of friends.
- Tomboy: Snarky and into sports.
- Women Are Wiser: One of the smartest members of the Casper trio.
- You Gotta Have Blue Hair: Her hair is blue.
The head bully at Scare School and Casper's arch nemesis.
- 0% Approval Rating: He certainly believes that he's popular, but nobody really seems to like him much. Even his henchman don't know why they hang out with him.
- Dreadful Musician: Thatch thinks he can sing, but to the others, he's horrible.
- Dragged by the Collar: Whenever he gets in trouble, someone (mainly Alder and Dash) drags him away by his cape.
- Flanderization: In season 1 he was sneaky, clever and better balanced. In season 2 he is whiny, not so scary and a lot more bratty and greedy.
- Our Vampires Are Different: He's a vampite, but isn't harmed by sunlight and doesn't have to drink blood to survive.
- The Dragon: Slither is normally seen helping Thatch the most out of the gang..
- Hair Decorations: Dummy Girl ties her hair with two big red bows.
- The Pig Pen: Mosshead doesn't bother much with hygiene.
Mickey and Monaco
Preppy Skeleton twin girls.
- Dumb Blonde: Mickey is a not-so-bright blonde..
- Single-Minded Twins: They are twin girls and they have basically the same personality.
- Those Two Girls: It's pretty rare to see them apart and they are extremely similar.
Alder and Dash
Scare School's headmasters. Dash, the head on the left, is very cunning and intelligent. Alder, the head on the right, is somewhat lacking in the smarts department but has ideas from time to time. But what they have in common is that they are both rude and manipulative.
- 0% Approval Rating: Not many people like them much, but they do have their loved ones who love them back.
- Cry Cute: The two of them both cry in the movie after reminiscing the good times they had with their Ankle.
- Even Evil Has Standards: They wouldn't punish kids if they did nothing to deserve it.
- Even Evil Has Loved Ones: They love their aunt/uncle (Ankle) and their pet bunny.
- Jerkass: Manipulative and impolite.
- You Have Failed Me: In "What Possessed You?", Kibosh sent them to the Chamber of Unspeakable Horrors for failing at turning Casper into a terryfing creature.
- Genius Ditz: Alder is rather incompetent, though he has his moments where he is the smart one, but not normally.
Scare School's gym teacher.
- Jerk with a Heart of Gold: He's stern and cranky, but nice when he isn't acting like that.
- Why Did It Have to Be Snakes??: He's scared of villagers with torches.
Casper's uncles and caregivers.
- Adaptational Nice Guys: Unlike most adaptations, they don't bully or look down on Casper for being kind, and when they're not pulling pranks on people, are actually pretty nice fellows themselves.
- Gadgeteer Genius: Stinky makes all sorts of inventions.
- Meaningful Name: Fatso is a Big Eater and the biggest of the ghosts and Stinky smells awful.
- Papa Wolf: Won't be happy about it if Casper is threatened.
- The Pig Pen: [[Meaningful Name Stinky is extremely messy. In one episode his stench becomes sentient.
- The Smart Guy: Stinky is good at inventing.
The much feared leader of the Underworld.
- Meaningful Name: He is determined to put the kibosh on Casper's friendliness.
- Used to Be a Sweet Kid: He used to be a friendly ghost like Casper when he was his age.
- Would Hurt a Child: Played with. He was never seen hurting a student. However, he has made things that would have hurt or even killed the students in season 1, plus Alder and Dash implied that Kibosh gives the students the same hideous punishments he gives to adult creatures, although Kibosh believes he is doing what's best for his people.
James "Jimmy" Bradley
Casper's best (human) friend.
- Friendless Background: Has no friends other than Casper (and later Mantha and Ra).
- Secret Keeper: Keeps a secret that Casper is friends with him.
- Wacky Parent, Serious Child: The Serious Child to Graham's Wacky Parent. While his father usually acts silly, he is usually laid-back most of the time.
Jimmy's father and Deedstown's Creature Catcher.
- Bumbling Dad: Jimmy's father, who is an airheaded and is very clumsy.
- Follow in My Footsteps: He wants his son to be a join him in the Creature Catcher business.
- Manchild: He can be seen hugging a teddy bear while Jimmy tells his scout trope a scary story in "Scare Scouts".
Deedstown's local bullies who love to make other children's lives hell, especially Jimmy's.
- The Bully: They make other children suffer. They especially target Jimmy.