I'm going to use this as an excuse to infodump about my 2012 + Portal AU a little bit, please forgive me- LMAO
Starting with Cave Johnson ! I think Mrs. O'Neil would be perfect for this role ! I want to give her character more than 2012 did, and I can absolutely see her being a CEO / in a management position, specifically in S.T.E.M. ! I know Kirby was also pretty intelligent (At least from what we saw from him in S1 to early S2-), but I like April following in her Mother's footsteps more ! Aperture Science would do all kinds of research under Mrs. O'Neil's leadership, and one of those things would be mutations ! I want this to be why the Turtles existed in the first place, as well as their direct connection to Aperture ! Mrs. O'Neil is honestly very cold-hearted to the Turtles in my head (Not exactly cruel, but sort of indifferent-? Like she won't react if they're in pain or uncomfortable-),, They're "simply experiments" to her, you know? She also has a strained relationship with her husband and daughter due to her being an incredibly busy woman-!
I think Kirby / Mr. O'Neil would fit Caroline's role best ! He doesn't directly work for his wife (Since Caroline was Cave Johnson's assistant-), however Mrs. O'Neil does leave him Aperture Science when she becomes ill (Possibly dies-??),, Something Kirby did not want and she knew that,, When he would help out at Aperture, it was usually to help with the Turtles cognitive abilities, given he's a psychologist ! Kirby was a lot kinder and gentler with the Turtles than his wife-! Eventually, due to declining health reasons, Kirby runs the facility for a short while- But it's mostly a title-! I think Dr. Falco (AKA The Rat King-) would be a good fit for Mrs. O'Neil's actual secretary at the time, and he'd be the one calling the shots rather than Kirby,, ! I don't have a definitive chain of events yet, but under Kirby's "leadership", a disaster happens (Probably due to Dr. Falco and his hubris-) that damages the planet, causing Aperture to be abandoned with the Turtles still inside-!
Dr. Falco could be Greg (Johnson's assistant who was replaced by Caroline-) I guess ! Dr. Rockwell could be Doug Rattmann? Maybe?
April would technically be her own character in this ! The daughter of the O'Neils who would occasionally visit Aperture Science sometimes as a child ! She had vague memories of the Turtles from back then, but genuinely thought she imagined them until reuniting with them years later (Upon revisting the laboratory to salvage supplies / materials during this apocalyptic situation-) ! I kind of started merging games with her, because she reminded me a lot of Elle from, "The Last Of Us" during all this !
Casey would be Chell ! I always give Casey a sad backstory, so he was given to Aperture Science by his Father for the child testing department (Something Dr. Falco facilitated-),, ! Of course it was for financial reasons,, He didn't meet April personally, only saw her in pictures, and he didn't interact with the Turtles back then- He was only permitted access in certain areas ! He remained in that Relaxation Vault Chell starts in during the beginning cutscene of Portal 1 for many many years (Even after the disaster- He practically knew nothing had happened-) ! The facility would provide him with food and water, so he didn't need much ! He always learned basic knowledge and academics in the vault ! He only leaves once it malfunctions and releases him from holding, where he then aimlessly wandered the laboratory until he crossed paths with the Turtles (Specifically Mikey and Raph-) !
All the Turtles were made into cyborgs, hence the robotic enhancements ! The goal was for them to be superweapons, of course- But the laboratory couldn't get far enough to actually utilize them-!
Mikey and Raph are Turrets ! I felt this fit them the most- For Raph it's the lethal aspect, for Mikey it's their deceptively innocent voice lines ! Plus they both feel like sharp shooters to me !
Leo is Wheatley ! He has such a charmingly dorky personality to me, which fits Leo, and I like Leo having this undertone of being in control even when it doesn't seem that way (Though I know Wheatley's story played out a little differently-) ! He's the one who takes care of Donnie's physical body and has the most access to restricted areas with the Labs !
Donnie, of course, is GlaDOs ! He runs the entire facility post the disaster via using his body as a power source (He made a lot of modifications on himself,,), using a robot body to act as his stand in (Kind of like Metalhead 2.0 from the Mutant Apocalypse Arc but has his consciousness inside it like Fugitoid-) ! So his robo self walks around the lab for him ! Donnie can control everything in Aperture, quite honestly !
He has an infatuation with April from the day they met, which is sad considering she barely remembered him and assumed she imagined him- But internalized that pedestal he put her AND her family on ever since, preserving Aperture Science as a love letter to them and hoping the act would put him in their good graces when they returned one day-! He lied to his brothers about that though, claiming it was "too dangerous" to leave (Which was technically a half life, given that was true at the time but later wasn't the case- They could leave by the time they turned 15-16 !). Leo found out eventually, but didn't say anything. It would've been too volatile to call Donnie out at the time, so he waited,, Raph and Mikey are pretty much oblivious the entire time-! Casey integrates into their group well (After Mikey always killed him though- LMAO), and the others enjoy having a new face around the Labs ! Donnie doesn't think he's that great at first, naturally-
Casey gets his Portal Gun as a result of an accident,, ! Casey (sort of) presses Donnie (His robo stan in-) about why they can't leave- He gets a little to close to the truth, which causes Donnie's physical body to panic, resulting in his robot retaliating against Casey believing he was in danger (Donnie's elevated heart rate and sweating sent signals to his robot body-),, So Casey lost his left arm,, And the only solution Leo / Raph / and Mikey could give him was a prosthetic arm with a portal gun attachment , since Donnie was having a mental breakdown over the whole thing and could help,, ! :')
Anyway ! Sorry for the yap ! 😭🫶✨