A boy sits at home, deciding to play through Pokemon FireRed again. He picks his starter and everything goes smoothly until after Celadon city. He'd just defeated the Rockets and obtained the Silph Scope and decided he would go and catch a Gastly. He searched the tower, trying to find one at a low enough level so it still had the moves he wanted, when he ran into a level 10 male gastly.
It's normal animation was gone, replaced with it's eyes growing bigger for a moment, the pupils shifting to look directly at the player. He brushed it off as perhaps his imagination, or some glitch he'd never seen before. He caught the Gastly without incident and left the tower. Training it on other pokemon outside, leveling it up. Every time he checked it's status that same eye animation occured.
As he went along through the game eventually his Gastly evolved into a Haunter. It too had it's normal animation replaced with the strange eye movement. Perhaps it was some odd thing unique to the Gastly line that happened with specific IV's or something. He thought little of it and wasn't about to abandon it now. After all, he put so much work into it, it would be such a waste.
Haunter grew and grew in power, proving himself a vital part of the player's team. Finally, he decides he wants to make it a Gengar. He takes his GBA over to his friend's house to trade. Another sign presented itself that something was off. After the trade, the Haunter on his friend's screen evolved into a Gengar. The player couldn't see, but as he heard the Gengar cry his friend froze with a look of terror. The player looked at the screen to just see Gengar sitting there, before the trade automatically initiated to put it back in his team.
The friend unplugged the transfer cord as soon as it was over and hurried the player out of his house. The player got home and looked at his Gengar's status, seeing nothing different except it too had the eye animation. He resumed the game, and everything progressed normally. Gengar was the star of his team, bringing him win after win. Even defeating the Elite Four again after the events at the Sevii Islands. With the game finally finished, he turned it off and went to sleep.
As he slept, he dreamed of eyes. Gengar's eyes. Staring at him, boring into him. He bolted awake in a cold sweat, and it was another hour before he finally fell asleep again with the same result of seeing those eyes staring at him. He tried to ignore them this time, but he felt a sense of dread that grew with every second until he woke again. Deciding to forgo sleep for now, he busied himself with chores until it was time for school.
The following evening he attempted sleep again, only to be greeted with those eyes. Once again he woke and decided he wouldn't sleep anymore. He stayed up all night, and all the next day as well as the following night and day. Occasionally he'd find himself nodding off in class or at home but the eyes woke him right back up. As the days passed he fueled himself with varying sources of caffeine to stay awake. Then he began to see the eyes while awake.
It was minor at first, thinking he saw them out of the corner of his eye. Watching him from somewhere unseen. Then whenever he looked at someone's face their eyes would change to those of Gengars. No matter what, whenever this happened they stared directly at him and he felt chills shudder up and down his body until he looked away. With every sleepless day these visions grew more and more vivid and frequent.
As he was sitting at his desk one day studying, he felt sleepy. Sleepier than he had in days. He took a few gulps of his coffee, but to no avail. His eyes were drooping fast, and the caffeine wasn't enough anymore. He struggled against his body's wishes, before at last collapsing on his desk and falling into slumber.
At first, there was nothing. Peaceful darkness, quiet and calm. Perhaps at last the nightmare was over. Then the eyes appeared again. But beneath them a wide, grinning mouth also materialized. It opened, and quietly spoke "You're mine now..."