Casper lives in an old house with his three uncles Stinkie, Fatso, and Stretch. Casper gets lonely a lot because he has no friends. Casper isn't like his uncles, he's sweet, favorable, and wishes his uncles would be too. Every time Casper thinks he's made a friend his uncles scare them away. Caspers family isn't normal, they're ghosts who haunts people.
Casper doesn't like scaring people because he doesn't believe in that, but his uncles are always pressuring him to haunt people. The house Casper lives in is now owned by a human named Carrigan, her dead father gave her the house. Once Carrigan visits the house Casper uncles scare her away. Carrigan hires a paranormal specialist named Dr. Harvey to remove the haunted spirits from her house.
Dr. Harvey and his daughter Kat came to the neighborhood because Dr.Harvey wants to find his late wife Amelia's ghost. The first day Dr.Harvey and Kat visit Casper house it turns into a disaster, because Casper uncles haunt Kat and her father. Casper wants to become friends with Kat but every time he tries his uncle scare her.
The machine only works on one person and they decide to use the machine on Casper to bring him back to human form. But things change when Casper uncles come with Kat dad, who's now a dead and has turned into a ghost. Casper lets Dr.Harvey use the machine so he can turn back human and be with Kat.
Casper's heartbroken that he can't be with Kat, but all a sudden he sees Amelia and she gives him one wish and he asks to be human for one night. Kat was throwing a party at Caspers house that night and she's surprised to see Casper in human form and they end up dancing together and they kiss. Amelia also visits Dr. Harvey and tells him to move on and that she will always love him and he needs to enjoy his life.