- Teenage Mutant Ninja Turtles: "what if... April O'Neal got mutated into a cat mutant at the beginning of TMNT (2003)" (TMNT 2003) [given by 3mtsims AO3]
they were doomed, surrounded by robotic stone-crunching monsters no higher than their knees, fighting beside four mutant turtle brothers, April never thought this was how she would go out, as she was working with Don to break through the computer defences a Mouser leapt at her, jaws wide to tear her apart, she instinctively swiped her hand out as if to batter it away, what happened surprised them all, her nails became long, sharp and claw-like, tearing the robotic monster to pieces, as she stared at her hand in a mix of awe and horror she suddenly felt her heartbeat pounding in her chest, so much that she gripped her chest and began to change.
The turtles continued to batter the robots away as they watched in awe, April grew a few inches with her muscles becoming a bit more defined, orange fur now covering her body, cat ears and tail sprouted from her head and lower back, her shoes tore open as she gained claws on her hands and feet, her teeth became sharper, her hair slightly wilder like a lions mane and her eyes became slit like a cat with the green shining more clearly.
Once her changes had stopped she was like a predator, she swiped at a few mousers that got close, destroying them like toys before turning back to the computer, the others tried to talk to her but it was like she was on autopilot, soon the mousers stopped, when asked what happened that is when April finally spoke, explaining that she was able to activate their self-destruct program, with that they all escaped before a massive explosion went off.
Now in the darkness of an alleyway, April began to panic and start asking what happened to her, the others were just as confused as her, they made it back to the layer and after explaining everything to Splinter Don started some tests with April on her D.N.A., they found traces of mutant strands like the families along with cat D.N.A., when asked how it could have happened Mikey spoke up, he said that one of those mousers had nicked him and she was a bit banged up, could his blood have mixed with hers, this made Don think and run a deeper scan with Mikey's bio, it was true, the mutant traces where from Mikey, April then said she encountered a cat during her escape from the Mousers, this lead to them concluding that some of the cat's hair must have stuck to her and mixed with Mikey's mutant blood that got into her systems and was activated from the stress of the fight, causing her mutation.
Mikey is sorry for this happening but April says none of them could have known this would have happened, she just wished she could go back up without needing to hide, that's when her fur and cat features receded into her body and she returned to her human appearance shocking them again, Splinter suggests she think of her cat form again and just like that she was a mutant cat girl once more, Splinter says she has the ability to shift between her forms, giving her the best of both worlds, he offers to help train her with her new abilities and fighting skills, she accepts.
Time passes with April opening her uncle's shop and training with the guys, getting better with her powers and computer skills, other than being more a part of the Turtle's adventures things go as they did in the original timeline, only with Casey saying her cat form is just as beautiful as her human form, and he has the marks on his back from her appreciation.