Work Text:
Many years ago, before the legendary rivalry between Sonic and Eggman, things were quite different.
Doctor Eggman or rather, Doctor Robotnik as he’s known now, is one of few humans on Mobius, to have ever been on the planet.
He was part of a team of human scientists and researchers that had been allowed to arrive on Mobius to study it.
It’s late one evening when Robotnik comes across a Mobian fox kit. It’s just outside of one of the towns. The kit is so young, barely older than five or six years old.
They are drawing something in the dirt. Upon closer examination, the doctor realises that it’s complex strings of algebra equations. Well above anything that they should know at this age.
That fact piques Robotnik’s interest instantly. Over the next few weeks, the doctor keeps seeing the fox kit.
One day, the doctor is working on the plans for one of the three robots that he has to complete a working version of by the time the team is set to return to Earth; when he catches sight of a fox kit watching him through the window.
After that first time, he catches sight of the fox watching through the window over and over again.
On the sixth day that the doctor catches the kit watching him work, he makes the choice to invite them into his workshop to watch properly.
Time goes on. Eventually, the kit (whose name is Tails, he learns) starts asking questions rather than just watching. If anyone else had been present, the doctor would have denied that he was properly answering his questions.
Somehow, answering the questions that no other five-year-old should even be able to consider let alone ask becomes actively teaching the kit mechanics.
By the time he and his team is supposed to return to Earth six months later, the fox has learned so much.
The other scientists and researchers return to Earth, Robotnik doesn’t. It’s around that time that Tails befriends Sonic and then, not long after, the doctor’s rivalry with Sonic starts.
It’s been years since then. Years since that time when Tails and Robotnik had been sat around various plans and other pieces of paper while the latter taught the fox the finer parts of mechanics.
Robotnik — Eggman now — and Sonic (alongside Tails, Amy, Sticks and Knuckles) have near-daily fights. Dozens of his robots are turned into scrap each week.
Tails doesn’t tell the hedgehog where or who he learnt mechanics from (after all, Sonic never asks). The fox isn’t sure if he should be grateful or insulted by that. By the time he wants to tell Sonic — who has every right to know one of Tails’ longest-kept secrets — the whole meteor brain-swapping thing happens and Sonic finds out by accident.