Casper the Ghost died from pneumonia at the age of 12. According to the backstory revealed mainly in the 1995 live-action film "Casper," Casper caught pneumonia after playing outside in the cold all day and night on a sled his father had bought for him. His excessive exposure to the cold led to his fatal illness. After his death, Casper returned as a ghost and haunted his family home, particularly staying close to his father. Casper's father, devastated by his son's death, created a machine called Lazarus in an attempt to bring Casper back to life, but was declared insane and committed to an asylum before he could succeed. Casper remained a ghost because he couldn't fully cross over, staying on to keep his father company and for other unfinished business.
