Casper is overly friendly and helpful, which is both his strength and weakness. He is quick-witted, being able to come up with speeches that convince people to go along with him. He is also independent, strong, never forgets who he is and is loyal to his friends.
Casper knows he is supposed to be scary, not friendly but he doesn't understand why people and creatures just can't get along. Casper's attachment to both the "fleshy" and creature worlds, while not quite belonging to either, often leads to problems at Scare School and he continuously faces the oppressions of Thatch, a vampire bully and the Headmasters, Alder and Dash, but he always finds the courage to face any obstacles heads on.
Casper is a small, white ghost with a round head that is almost as big as his body and a somewhat pudgy body. In the movie he had violet eyes, in the first season of the series his eyes very light blue while in season 2 they are dark blue and unlike his family, he has feet, but his legs morph into a ghostly, genie-like tail.
When he hangs out with Jimmy in Deedstown he wears a blue hoodie with the hood always covering his head, navy blue jeans and black sneakers to avoid scaring anyone.
Casper is extremely friendly and kind and isn't afraid of being himself. He is always willing to help people, even if they are his enemies. He is willing to go to great lenghts and take right risks to help his loved ones. Casper sometimes has low self-esteem as seen in "Slugby". Although he can get scared easily, Casper is also very brave, being possibly one of the very few living beings that isn't afraid of Kibosh.
In season 2, Casper is somewhat harsher and doesn't seem so upset with the idea of scaring humans as he is even becoming a better student than Thatch.
- Ghost Physiology: As a ghost, Casper possess various abilities.
- Body Manipulation: Casper can manipulate his lower body by transforming it into legs to walk and to have a ghostly tail when flying.
- Fly: A standard ghost ability.
- Intangibility: Casper can phase through solid matter, as well as people including monsters. When he phases through people or monsters, like what he did to Thatch, they fill a sudden chill.
- Invisibility: Casper can turn invisible to hide from people and for stealth approaches. He can also be intangible as well as invisible as the same time.
- Possession: Casper also has the ability to control people's bodies. Although he doesn't seem to quite master it, as seen in I'm Not A Hero he took control of Thatch's body but he was still talking, meaning Casper can only control the motor functions of the brain.
- Kindness: Casper is extremely kind, up to the point were he literally can’t resist helping people.
- Scaring: Casper is exceptionally skilled at scaring humans, even when he isn't trying to. His ability to scare may be better than Kibosh's as seen in "Accidental Hero".
- Leadership: Casper has shown notable leadership skills in several episodes such as in “Power Outage (Part 3 and 4)” and “Slugby”.
- Bravery: Casper is very brave since he seems to be the only creature who isn’t afraid of Kibosh and wasn’t intimidated by the school faculty’s scary act in “Slugby”.
- Strength: Casper is rather strong physically as he is able to carry other kids in his arms thourgh long distances without straining in several episodes such as "Paramedic Paranormal".
Casper acquired many allies due to his friendly, helpful personality; however, his friendliness also resulted on him being looked down upon his fellow creatures.
Stretch, Stinkie and Fatso are Casper's uncles and caretakers. The Trio love and care for him very much and Casper cares back. The Trio can be tough on Casper when the situation demands it and let him do what he wants othewise. Casper enjoys his uncles' company, although he doesn't like it when the Trio try to get him to be like them.
Grandma Smoochy is Casper's grandmother. She loves her grandson very much and Casper loves her too, although he seems to dislike being kissed by her.
Spitzy is Casper's great aunt. They get along well and spent all the time they were together in the Valley of the Shadows with each other.
Ra, along with Mantha, is Casper's best creature friend. They get along very well, though they do argue at times. Ra often has to look out for Casper due to his naiveness, although sometimes it is the other way around.
Jimmy is Casper's best human friend. Casper sometimes sneaks out of school to hang out with him and could do anything for Jimmy, even if that means disobeying his uncles or risk being expelled from school.
In the first season Wolfie was also friends with Casper, although the relationship seems on and off as he was not seen in Casper's company as often as Mantha or Ra.
Casper and Cappy got along great ever since they first met since Casper complimented Cappy. They are close friends and could do anything for each other.
Casper doesn't associate with them a whole a lot but he does seem to get along well with as acquaintances since the girls were never mean to him at all;in the episode Ship in the Bottle in Mickey and Monaco both complemented and praised the ship in the bottle that Casper created for a school contest as did other students who also admired his work, and when the bottle went missing because of Thatch swiping it unseen the twins and other the classmates all helped Casper to go and look for it. Also in just the episode Last Dance did Monaco and Mickey show strong feelings of affection for him when they both apparently asked him to each be their date to the school dance and he agreed to be not wanting to hurt their feelings by rejecting them at all,but this was the only time the twins ever behaved in a love-struck way towards him.
Thatch became Casper's rival from the moment they met. Thatch hates Casper because of his friendliness. Despite this, Casper often helps Thatch if he is in trouble. As the series goes on, Casper acts a lot more aggressive towards Thatch, to the point where he placed a curse on Thatch for embarrassing him ("Davey Jones' Locker") and almost gets him expelled from school ("I'm Not A Hero").
Mosshead treats Casper slightly better than his friends ever since "Messy Business at the Manor", where Casper invited Mosshead over to his house for vacation when he had nowhere else to go although Casper soon regreted his decision due to Mosshead's poor manners but when Mosshead intended to tell their classmates about Casper's friendship with Jimmy, Casper snapped and told him off for being "a jerk". Mosshead apologized and the two make up. In "Slugby", Mosshead gave Casper a piggyback ride after they won the Students vs. Teachers game.
Despite being on bad terms with both Alder and Dash, Casper acts civil towards them since they are his school's headmasters.
Casper strongly dislikes the Normans due to them constantly bullying Jimmy. The brown-haired Norman was the first human Casper willingly scared after Norman bullied not only Jimmy but the entire school.
Unlike most creatures in the Underworld, Casper doesn't seem to be afraid of Kibosh and will to stand up to him when necessary, although he still respects him.
Kibosh admires Casper's bravery and is partial to him since he sees himself in Casper and confided in him that he used to be friendly before being the leader of the Underworld.