Oroku Saki is born somewhere in Kyoto, raised in a very noble rich family that's super loyal to the shogunate. As a teenager by the age of 15, Saki stumbles upon a crashed Utrom ship while exploring the woods. A somewhat sheltered & lonely child, Saki befriends the benevolent Utrom but doesn't tell the rest of his family.

  Years pass, and Saki turns 20. Tensions arise within the Utrom group, as they're getting no closer to returning to their homeworld due to how primitive Earth is. This eventually leads to the formation of The Kraang, who want to take the conquest route & colonise Earth to suit their needs, while the rest of the Utrom don't want to disturb the planet's natural environment & decide to wait until technology on the planet improves. Unsurprisingly, privileged & militaristic Saki sides with The Kraang, seeing the Utrom as weak-willed & cowardly. The Kraang accept Saki's aid, but see him as a mere pawn to their greater plans.

  The Kraang create the first prototype of mutagen ooze, intended to mutate the Earth to greater resemble the Utrom homeworld. But they need to test if it works, so they enlist Saki to deliver it to the central water fountain in his village, telling him that it's a divine medicine that will bless those who drink it with strength & power, revolutionising his village.

 Things do not go as planned. Wanting this divine power all to himself, Saki drinks all the ooze first; but instead of turning him into a god, his skin turns purple & scaley, three red horns burst from his forehead, his hands become claws; Oroku Saki becomes the first mutant. The people around him scream in fear. Saki's own family turns against him, denouncing him as a demon from hell. Furious, Saki returns to the woods, demanding an explanation from The Kraang. The Kraang say it's his fault for not following orders.

  Saki is livid at being betrayed by everyone he's known, and with his newfound strength thanks to his mutant form, he goes on a rampage; first driving The Kraang and the Utrom out of the forest, then returning to conquer his old village, declaring himself their new leader. He kills everyone in his old noble family & claims their riches for himself. From now on, he decrees that this village will be the home of the newly-founded Foot Clan, and he christens himself The Shredder.

  Meanwhile, Hamato Yoshi is born as a peasant somewhere in the Iga Province, training as a ninja of the Hamato Clan from a very young age & eventually achieving mastery by the time he's in his early 20s; proudly helping defend his village alongside the rest of his clan.

  Yoshi's idyllic life can't last forever, though. The rival Foot Clan soon comes marching into his hometown. When the village refuses to submit to The Shredder's command, he orders the Foot Clan to attack, destroying everything & everyone that Yoshi's ever known. During the battle, The Shredder slashes across Yoshi's chest and cuts off his right leg. Howling with pain, Yoshi retreats to the edge of town, near the woods.

  But there's something... unusual about his wounds. They're glowing; a green, shining liquid burning at the edges of his skin. A curious black rat licks at Yoshi's wounds, and suddenly fur sprouts out from his skin, his entire body structure & DNA is being rewritten, and Hamato Yoshi turns into a giant rat. Well, the glowing's stopped, but he's still bleeding.

  And then... there's a light. A circle of blue, swirling impossibly in the space next to him. A portal.

  Desperate, with nowhere else to go, and more than a little bit delirious from his injuries, Yoshi tumbles into the light.

  It's the year 2003. Imagine you're Kirby O' Neil, humble scientist employed at T.C.R.I Headquarters, doing some routine solo tests in the middle of the night for the company's time window project. And then a giant human-sized anthropomorphic rat comes tumbling out of the portal, speaking nothing but very confused Late Middle Japanese, bleeding from a freshly amputated leg and giant slashes on its chest. Obviously, you spit out your coffee and stain the very expensive window in shock.

  Kirby closes the portal & frantically calls his superiors; a bunch of nameless weirdly identical-looking guys in suits, who quickly take charge of the situation, tranquillising the rat & carrying it to the infirmary to heal its injuries. Curious about the rat, especially considering it probably has some level of intelligence considering it could speak Japanese, Kirby follows.

  Yoshi wakes up, cold and afraid, in what's basically a glorified prison cell, but all white and shiny. He has no idea where he is, but is thankful his injuries have more-or-less healed. He takes stock of his new form, equal parts fascinated and frightened by his rat-like appearance- as well as the prosthetic leg he's been outfitted with. Then a man visits through the door, speaking a strange language he does not understand.

  Through some charades as he repeatedly gestures at himself while repeating the syllables Kaa-bi Oni-l, Yoshi realises the man's trying to tell him his name. Yoshi shakes his hand, introducing himself as Ha-ma-to Yo-shi.

  Over the next two years, the curious though uninvasive & friendly Kirby, and the nervous & lonely, but skilled & determined Yoshi, grow closer. Kirby visits frequently whenever he can, and Yoshi slowly learns modern-day English; helped by what little he knows about Early Modern English. Kirby gives Yoshi the nickname "Splinter", seeing as he's technically representative of a splinter in time. Splinter's time in T.C.R.I is, uh... not great, though, seeing as he's a giant talking intelligent rat, being subject to lab experiments that range anywhere from incredibly boring to incredibly painful. Splinter & Kirby make plans to smuggle him out, but they're only pushed to actually do it, when...

  Four turtle eggs have been infused with half of Splinter's DNA. Specifically the human half. In partnership with a mysterious client known as the Purple Dragons, T.C.R.I wants to replicate the affects of the mutagen ooze & create super soldiers.

  This is the last straw. No way are they going to let them raise child soldiers, mutant or not. Stealing the four eggs, Kirby & Splinter sneak out of T.C.R.I headquarters, hiding out in Kirby's apartment. Kirby denies any connection he has to the lab rat's disappearance, but hands in his letter of resignation anyway, for definitely totally unrelated reasons. Meanwhile, for the first time, Splinter meets April O'Neil, Kirby's daughter, only a few weeks old, recently born at the cost of her mother's death.

  From 2005 to 2007, Splinter ends up being Kirby's roommate & they have a kinda sweet gay domestic situationship going on. They're not dating, but they're also not not dating if you catch my drift. Splinter takes up painting & learning about art history as a hobby, since there's not much else to do since he can't really go out in public. In 2005, the Softshell Turtle egg hatches first; and Splinter names the little mutant hatchling Donatello. This is followed by the Loggerhead Sea Turtle & Red Eared Slider egg in 2006, named Leonardo & Raphael respectively. Last, but not least, the River Cooter egg hatches in 2007, named Michelangelo.

  While Splinter & Kirby love each other's presence, and the young turtles & April get along surprisingly well... having five entire children in one tiny apartment, four of which are rowdy mutant turtle infants who are now becoming toddlers, is... not a great experience. Eventually, the two families choose to part ways; though not before Kirby gives Splinter a gift: a dark blue kimono, custom-made & delivered directly from modern-day Japan, tailored to be durable, comfortable, and as long-lasting as it can get. They hug & say their goodbyes.

Okay I admittedly don't actually have much here, but here's what I do have:

• Mikey, who is 13, isn't allowed to go to topside missions with his brothers because he's so young. So he sneaks out as an anonymous, masked vigilante known only as "The Titan" (Reference to the Turtle Titan from older iterations) and ends up kicking a lot of bad guy butt, much to the confusion of his brothers who are wary of this powerful stranger. 

  They find out his identity when he accidentally tries to bite off more than he can chew- Mikey's a bit of a glass cannon- he can certainly pull a punch, but doesn't have much endurance. Later on they all decide it's best for Mikey to join them on their adventures, because if he's going to put himself in danger anyways, might as well do it with supervision and support.

•   April and Casey are students looking for interesting stories to report for the school newspaper. April meets the turtles after investigating rumours of strange monsters roaming the city.

•   Donnie has a one-sided crush on April, who doesn't reciprocate on account of being a lesbian and having a thing for Casey. Because this isn't the 2012 series, Donnie genuinely just backs off & works to get over his crush, as he respects April's desire to just be friends, and having her company at all is more than enough.

•   The turtles meet Leatherhead, and find out about the whole T.C.R.I-creating-mutants-with-the-Purple-Dragons lore from their dad, who urges them to take the story as a warning and not to go seek them out. Meanwhile, Leatherhead is given a place to stay at another area of the sewers; not the lair, but not a far walk from it.

•   Needless to say, but the turtles ignore Splinter's warnings and go investigating. They meet, befriend, and fight more mutants along the way, and those that aren't malicious enemies and need a place to stay become Leatherhead's neighbours.

•   This slowly but surely becomes Mutant City, a secret place for non-humans to seek refuge in the sewers.

•   MEANWHILE, Casey's been worried about April getting more and more absent from school, and she won't tell xem the truth, even about the bruises she now bears from all her adventures with the turtles. Suspecting possible abuse, Casey sneakily follows her; and is absolutely terrified and gobsmacked when xe runs into Mutant City. ...At least xyr mask is useful in helping xem fit in with the non-human crowd.

•   There's probably some kind of confrontation between Casey and April about everything later???? Casey is pissed that April's been putting herself in danger without telling xem, because they're supposed to be best friends and partners, while April's frustrated because how the hell was she supposed to tell someone about all the mutants and ninjas and fighting without just looking crazy?! They split ways for a bit and need to cool off. Then they both get kidnapped by The Kraang, who've been running T.C.R.I, and reconcile while breaking themselves out. They're still a little mad at each other, but they also understand each other better now.

•   Oh yeah plot twist T.C.R.I is The Kraang and the Purple Dragons are actually part of the Foot Clan and want to bring back The Shredder from Feudal Japan.

•   Karai is The Shredder's modern descendant instead of his direct daughter. He still ends up treating her like a daughter anyway, and has enough of a soft spot for her to be his second-in-command, hear all his dramatic evil monologues, as well as see him in a more casual outfit without his full armour.

•   Also somewhere along the way Splinter and Kirby reunite and continue their weird situationship without actually confirming to anyone if they're together or not. Part of this is to mess with their kids who are tearing their eyeballs out anytime they see their parents being overly sappy with each other.