Jon's mom rushed her off to the bus stop after a short breakfast. As Karyn walked up to the bus stop and saw another catgirl there, dressed in Jon's clothing, her jaw dropped.
"Jon!" she gasped. "Did...did you...?"
Jon nodded. "Obviously, yes I did." Her new voice sounded strange; much higher and softer than it had when she was a guy. "Mom said it wears off though. I was always under the impression that it was permanent. Not that I'm complaining. How do you deal with these things anyway?" She indicated her new breasts. "I couldn't get down to the bus stop without them bouncing around all over the place."
Karyn snickered. "After school I'll introduce you to this little miracle called a 'brasierre,'" she said.
"Wha...I'm not wearing a bra!" Jon protested.
"If you're bothered by the bouncing, you will," Karyn replied. "Besides, if it wears off, it'll only be for a little while."
They got on the bus and spent the rest of the ride in silence. What did Mom mean, "your sex doesn't change back?" Jon wondered. Did that really happen? Could she really be stuck as a girl? She hoped not.
When they got school, one of the hall monitors grabbed them and directed them to the nurse's office. "Your mothers called, you two," he explained. "They explained the situation, so we knew who to look for. There's just a little paperwork to fill out and a test to run, so it'll only take a couple minutes."
In the office, the school nurse met them. "Ah, Jon and Karyn!" she exclaimed. "I'm glad your mothers called; you really should have done so yourself, so just remember that for next time, OK? I'll need a blood sample from both of you, and then we've got some paperwork to fill out." They both got pricked and the nurse stuck the samples into a small machine.
As the samples were being processed, the nurse ran them through the paperwork. Karyn's was minor, just a note of the change in hair color and a check next to the "cat-person" category in a list of common changes. Karyn noticed that there was a write-in "other" option; she wondered what sort of alterations had prompted the need for that.
Jon's paperwork was somewhat longer; the "cat-person" box was checked, as was the "transgender" box, with an "F" put in the "sex" entry. Then her height and weight needed to be measured and her new hair color noted. "We'll skip the name-change bit, I'd guess?" the nurse asked. "The changes usually only last for a week or so, so I assume you're not planning on changing your gender identity, right?" Jon nodded.
The machine beeped, and the nurse went back to get the results. She returned with a solemn look on her face. "Jon," she said, "Karyn, I have something to tell both of you."
Jon moaned. "Oh no," she said, "my sex isn't changing back, is it? Mom said..."
"Not quite," the nurse responded. "That happens in about 25% of transgender cases. Actually, you and Karyn have something even rarer. It only happens to about 6.25% of people who change."
"What is it?" Karyn asked. She and Jon listened apprehensively.
"Well," the nurse hedged, "it's...you're not changing back at all. Your changes are permanent."
Jon sat there in shock. Karyn was a little more clear-headed. "Um," she asked, "can...is it possible for us to change if we get infected again?"
The nurse shook her head. "No. This is the rarest form, and the only one which the immune system can effectively analyze for prevention against. Technically, if you caught it again, you could change, but your body's natural protection against diseases will prevent you from even catching it. I'm afraid both of you will be like this for the rest of your lives."
