Eris liked to make trouble. It wasn't just teasing her brother, for while being stronger than Pluto certainly made it easier, it was also boring, for Pluto never reacted to anything. Ever. Eris preferred a challenge; if she was going to cause an uproar, she wanted to earn the right to sit back and watch. Perhaps it was eccentric of her, but she preferred to sow the seeds over time. So if sometimes she pushed and sometimes she pulled, or spent time quietly plotting, it was all in service of a greater goal.
Then, one day, someone nudged her. There had been a disturbance she hadn't caused, last time she visited, but everyone had said it was fine, including Pluto, and she'd trusted them. She should have known Pluto would have just gone along, not knowing anything was wrong until it was too late; she knew him best, after all.
She devoted what time she could to finding out who knocked her off course, but it didn't happen again, so she really had nothing to go on, and she couldn't abandon her other plans.
Except someone had gone and pushed them too, and they were out of place.
Eris was not amused, and as every attempt to find out who was bullying her family failed, she grew more annoyed. She was the only one allowed to sneakily adjust their orbits, damnit, and had worked so hard to hide her plans; that someone could just undo that made her feel the same way as she did when Pluto reminded her that he was actually older.
She was approaching that same spot again, with some trepidation, but this time there was no pulling, no sense of loss of control, just a familiar shadow, dark as night.
"Hi Dad," she said, and smiled.