The Scaredy-Cat Ghost was a ghost with a silly voice that was very afraid.
The Scaredy-Cat Ghost was a spirit recently trapped by the Ghostbusters. It was volunteered to demonstrate the Dimensionometer, an alternative to putting trapped ghosts into the Containment Unit by permanently banishing entities to another dimension.
When Peter Venkman went inside to find Egon's soul, the ghost appears to him and begs to be taken back. This Netherworld dimension scared him. Peter agreed and asked if he'd seen a human soul. The ghost told him that he saw one soul and tells him where it was, just over a nearby hill. Sure enough, it was Egon's soul. Peter opened a trap and let the Scaredy-Cat Ghost jump inside.
He is a very cowardly ghost. For example, he kept on pleading "No!" when the Ghostbusters put him into the Netherworld portal and when Peter Venkman found him, he begged him to put him in the Containment Unit, saying that the Netherworld was too scary for him.