This certainly was creepy. It fits any of the Ghost Pokemon, particularly the ones that tend to be found in cities. I was personally thinking of Haunter. The use of "baby" as the name the ghost gave the trainer added to the creepiness. "Baby" is such an intimate pet name in relationships, and having the ghost see the trainer that way made the ending more effective.
Why aren’t you screaming anymore?
You were going for creepy, and you reached it with this one-shot. I hope to see more from you. Maybe the next time procrastination strikes?