Oddly-Expressive Kraang

There was an oddly-expressive Kraang in one episode of TMNT 2012 s5, so I am wholesale stealing them. That character is canonically this one, and that's just true.

TL;DR A kraang that was knocked from the control of the hivemind in a fight against Splinter. After years of hiding in the sewers and unsuccessfully trying to find other escapees, they elected to try escaping into another dimension. They got stuck in the middle of the Triceraton invasion in the 2003 universe. They were rescued by an EPF agent, who then recruited them to be part of her squad. Now they've been working with her in the dimensional anomalies division for over a decade.

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This Kraang has a naturally strong resistance to psychic powers, but not enough that they were immune to Kraang Prime's control. While they were still caught in the hivemind, they did display small quirks of individuality. 10 years ago or so, they were part of a squad that was sent to hunt down some accidental mutations on earth. They found the subjects, a rat and some juvenile turtles, and after repeated confrontations came very close to killing the turtles. In a rage, the rat beat them down until their mechanical body was dented and struggling. Unintentionally, the rat's vicious attack ended up being the last push they needed to snap them out of the mind control. Suddenly aware, and afraid of being re-controlled, OEK dragged their damaged Kraangdroid deeper into the sewers to hide while they attempted to repair it.

They spent a year just hiding and rebuilding, never daring to leave their safe little hiding spot. When they started to become dangerously hungry, they had no choice but to venture out. They made a handful of heists back to Dimension X for food, looking for a sign, any sign that there were other escapees like them. They never found any, and realized they were alone. It was then that they decided they would never be safe, at least not in this world. They formulated a plan to sneak into the Hall of Portals and go through the first alternate-dimension portal they found. The plan went a little haywire, and they ended up accidentally falling through several at once.

Once the multiple portals were done throwing them around, they got spat out into the 2003 universe, right into a Triceration ship in the middle of their invasion. An EPF operative discovered them not too long after, and, assuming they're a human, refused to leave them alone. The fight to escape the ship together is life-or-death, and they begin to form a bond as they go. Then, OEK accidentally outed themself as an alien, and the operative nearly turned on them right then and there. But they are swarmed with enemies, and have no choice but to continue working together.

By the time both finally made it back to solid ground, the operative couldn't bring herself to see OEK as an enemy, regardless. She resolved to get them on-boarded into EPF. OEK didn't really know what else to do, so they trusted her. This gets them taken as a test subject for a few months. Eventually, though, she pulled through, and they're trained in to join her squad. Her name was Castle, and she led a field squad specializing in investigating and containing cross-dimensional anomalies.

Castle helped OEK pick the name Franklin Ritter, taught them to fight, and they've only grown closer since. They've been in EPF for over a decade, and they only grow more indistinguishable from a native human as time goes by (though they would struggle to fit in with civilians outside of EPF.) They grow embittered toward their own kind and fully loyal to EPF and its ideals. Recently, Castle's squad has been hunting down an unidentified alien that appeared in a blip, and that's about what they've been up to in recent times.