Leatherhead's Owner
 

Will anything become of Leatherhead's original owner? We once speculate he was in fact Casey Jones.

What we do know is that due to Leatherhead's age(slightly older than the turtles in human years), his owner(whom we can assume was around 13-15 in the flashback) would have to be an adult in the present day narrative. I would love to see this touched upon again at some point in the series, as Leatherhead's memories of his kind owner are what fuel his will to protect the humans.

I don't think he'll appear again.

With the resemblance in the flashback, make the old owner Casey's father... ;) (And maybe they were fairly young when Casey was born.)

I wouldn't mind Leatherhead's owner becoming this show's version of Mondo Gecko.

Same here. With the character design, I could see it.

I'd very much like to see an episode concerning the relationship between the two. Leatherhead is a powerful character with a pretty charming origin story in the Nick universe.

That being said, I highly doubt they will go to such lengths. Leatherhead's past was quick, beautiful, and appropriately simple. I'd hate to see that image marred by a poorly written episode regarding the whereabouts of his beloved human boy. Sometimes, things are best left in the depths.

Yeah... It would be nice to have Leatherhead reminisce on his days as a pet... Maybe even have him contemplate how his life has changed so dramatically... Realizing that while he does miss his boy, if they were never separated he wouldn't have become the hero he is today...

Seeing them reunite after all these years would be a truly fantastic thing to see... The reactions that would come from both of them is something I've often contemplated... But I do see your point... Leatherhead has fond memories of his boy, and it's those memories that shaped him into who he is... Perhaps it's best if his last memories of him are of a time when the two were inseperable.