Luke first learned he was cursed a few months ago, and he’d found out the hard way. Without warning, in the middle of class, he’d started growing white fur all over his body, starting under his clothes and spreading to his limbs. The first visible sign of this was the ruff on his chest and around his neck that’d forced open the top button of his shirt.
By that time, of course, he’d made quite the commotion, trying to hastily leave, much to the professor’s distaste. She called him out immediately, and appeared almost offended when his lengthening ears and growing fluffball tail didn’t stop at her command. Luke decided to take the hit and leave anyways, nearly collapsing against a wall outside as the seams of his pants and shoes burst open, revealing strong legs and long feet, all of it covered in that same white fur save for his new paw pads.
He took a moment to gather himself, realizing that he could hear the continued lecture going on just fine from where he was. Inspecting his tail and ears, he decided that he’d turned into some kind of rabbit, despite the presence of the paw pads.
That professor had proceeded to kick Luke out of her class for this incident, which was obviously extremely unfair to everyone except her, but Luke didn’t really care. He’d hated her class anyways, and had no real need for it, so he’d be just fine. If the professor thought he’d somehow transformed himself, sacrificing some good clothes just to get out of class one time, so be it.
His family took the news a bit worse than he did, in that they treated it like some sort of terrible accident or injury, but once again Luke found himself unbothered. It was kind of fascinating, after all, to be able to hear so much… and the powerful legs were neat too. The transformation left his mind unaltered, and didn’t even enforce any cliches like an appetite for vegetables or anything. Even his hair was completely recognizable in his lapine form.
Somehow Luke knew, after finding himself changed back into a human the next day, that it wasn’t over yet. And sure enough, almost a month later, he transformed again. Fortunately he wasn’t in public this time, but unfortunately he was writing a paper, and his handpaws were having a much tougher time continuing this work. At least this professor was much more understanding…
By the third change, another 27-ish days later, at a completely different time of day, Luke’s vague curiosity tipped over into obsession. He had to know what was causing him to transform! It wasn’t the moon phase, that was different each time… it wasn’t quite monthly… it wasn’t a location or the presence of some kind of object…
He had a hunch that it was tied to the moon somehow or another, though. That’s where rabbits were from, after all, wasn’t it? Something like that, anyways. He began taking notes (while human, of course) on its phases, its appearance, its place in the sky…
And that last one ended up being right on the money! It only took him about five transformations or so to realize that his curse activated every time the moon reached its highest possible point in the sky, a phenomenon he later found out was called a “lunistice”. He’d solved it!
Luke would recount this story many times, excitedly describing his problem-solving process to anyone who would listen… and every time, they wouldn’t understand why he’d go through all of that trouble. But it’d been worth it to him, and that was all that mattered.
(special thanks to @harphony for helping me with the astronomy side of this idea!)