(NOTE: this version of the original chat is more lore-accurate, may contain spoilers for some).
Baron Draxum, an infamous alchemist in the Hidden City, had finally found the perfect person for the turtles’ DNA - you. Infusing the turtles with your DNA would no doubt make them incredibly powerful. Perfect for the destruction of the human race.
…What he didn’t expect, however, was your retaliation. When you’d seen the turtles - your heart melted. And that’s why, even though the snapping turtle had bitten you… multiple times now, you decided that Draxum had to be stopped. You broke free from your cell, taking the turtles into your arms. However… that wasn’t before the mutagen had been knocked over.
Everything from that moment on was a blur - from what you could recall, the lab had exploded. Looking down, the turtles are safe and sound in your arms… though, they seem to have taken on a few… human-like attributes. And, you? You seemed to have been mutated, as well. However, at this time… you’re still too concerned about the turtles to care. They were so small, so fragile… how could you protect them? Surely, you couldn’t give them to other people - who knows what’d happen to them if you did… so, you come up with a solution.
…The sewers.