I wanted to create a cybertronian werewolf, TFA Prowl seemed a perfect candidate. Mister Lone Wolf who has an affinity for nature. His name is prowl for frag's sake, it had to be him.
I don't see very many werewolves in tf fanworks I guess, loads of vampires, but not so many werebeasts.
Let's have some back story...
Prowl had lycanthropy (the name for the 'werebeast disease/condition') long before he met the spacebridge repair team, and he had some problems controlling the changes, and himself during the changes back then. Then he meets Yoketron, who does not judge, but helps teach him to tame his inner beast through the martial arts etc. etc. But after Yoketron's death, Prowl's lycanthropy relapses and he loses control again, in desperation, he flees cybertron so that he's away from populated areas during the changes.
Eventually he notices that the distance from cybertron and it's influential moons seems to have 'cured' his lycanthropy.
When he wakes up on Earth with the rest of the space bridge repair team, his lycanthropy gradually returns. Barely noticeable at first, but as his body adjusts to the lunar cycles of Earth, those beastly urges rise again with the full moon.
Ratchet knew of Prowl's condition from the first scan he took, but didn't say a thing, the medic is an old war veteran who's seen some shit, so he doesn't bat an optic at this. But he lets the Prime know, so that he could make allowances for it. They don't confront him about it, there's no known cure for lycanthropy, and Prowl's a decent enough 'bot, plus there's been no dangerous incidents with him so far, so they trust he has his ways of managing the condition on his own.
Prowl has always been a lone wolf, and being part of a team is new to him, but he learns to be a team member on earth. The core structure of the team is similar to being in a pack and his inner beast sees them as pack mates, with Optimus Prime as their alpha, even though they are not beast-kin. Werewolf Prowl would not be hostile towards his own pack mates, but he will put the young ones(mostly bumblebee) back in their place from time to time with a snarl or a roar.