Some things change

In the beginning, it was just me, Marcus, Lily, Josie and Brandon. Marcus and Lily were sports nuts, being in the gym for half of each day. Josie was more concerned with studying, so spent most of the daylight hours revising before partying at night. Brandon was just an all-round nice guy, he had a whole host of friends. I was quite similar to Brandon, but I was only friends with the people I have just mentioned. Then things started changing...
It started when me and Marcus were coming back from a night of revelling. We heard a scream from Lily's room and rushed in to find the porky Brandon standing next to her bed.
"I heard the screams, but when I rushed in here, she was gone, guys", he whispered, "the sheets are torn, I wonder what did this?" he carried on to say.
"Beats me, but it must of had sharp claws" I said, noticing a gouge in Lily's dresser.
"Let's hope she finds her way back here" said Marcus, "but now we all need some sleep". So we went back to our rooms, resolving to look into it properly in the morning.
In the morning, I told Josie about what had happened, and we were talking about it when Brandon arrived, with a sullen face.
"How's the investigation goin' buddy?" I asked
"I haven't found anything we didn't find last night, but we may have a bigger problem" he replied.
"What's that?" I asked.
"During the night, Marcus disappeared" he whispered. That explained his face. "There's more" he continued "I found a note in Marcus' room saying that whatever took Marcus and Lily is after the rest of us as well".
"Oh dear" whispered Josie " I think tonight we should all sleep in my room". We agreed on that.
That night, Brandon and I brought sleeping bags into Josie's room. We fit in it easily because Josie had the biggest room.
"I doubt it'll try and get us if we're all together" said Josie from her bed "It'd be too risky".
We settled down to sleep, leaving the lights on dim because it would have been pitch black otherwise. Just as I was about to fall asleep, the lights failed and Josie screamed, followed by a growling sound. When the lights came back on, Josie's window was open and Josie was nowhere to be seen. Brandon and I stared at her empty bed practically all night and then continously had nightmares when we did fall asleep.
The next day, I was sitting in the cafeteria having lunch when Brandon came up to me.
I need to talk to you in private" he said.
"Why?" I asked
"I can't tell you in public, meet me in my room in an hour and we'll talk there" he replied and he then ran off again.
I met him in his room at the time we had agreed. After I knocked, he opened the door and ushered me in. We then sat down on his beanbags.
"What's this thing, then?" I asked "and why couldn't you tell me in public?"
"I couldn't tell you in public because if someone heard me, my reputation would be ruined" he replied "and I wanted to talk to you about this" he said, pulling out something that looked like a big wolf's claw.
"It's a wolf claw" I told him.
"I know, I found it in Josie's room" he replied "there is another thing, though. I did some research, and it's impossible for a wolf to have this big a claw, the only thing that could have this claw is... a werewolf."
"A werewolf!" I replied, incredibly shocked.
"Uh-huh" he said "but now we should get to class, I'll do more research later." And with that, he walked out the door and I followed.
The rest of that day was pretty uneventful, apart from the science teacher accidentally dyeing his face green after a reaction went wrong.
I was strolling around the lounge the next afternoon, when Brandon came up to me, looking very excited.
"I think I might have found a clue about the werewolf in Josie's room" he said
"What?" I asked
"I'm not sure what it is, but writing appears on the claw when you hold it up to moonlight" he replied "I'll show you tonight". And, with that, he hurried off.
That night, I was lying on my bed when I heard a knock at the door
"come in" I said, and Brandon entered.
"Come on, I've got to show you the writing" he said, beckoning for me to follow, which I did. When we got to Brandon's room, he quickly opened the door and pulled me in.
"Where's the claw?" I asked, confused.
"You really believed me..." answered Brandon
"What are you talking about, Brandon?" I asked
"I left you enough clues, how I was always at the scene of the crime, how I never let you see anything I found and I always left my initials carved in the sheets" said Brandon.
"What do you mean, you left me enough clues?" I asked again
"Let me show you" sighed Brandon. At that moment his body started to change, and in about ten seconds, there was no Brandon, only a massive wolf-like creature in his place.
"You took them, you're the werewolf!" I just managed to say.
"Correct, Jack, and you're next!" yelled Brandon, lunging at me. I felt a searing pain in my shoulder and then I blacked out.
I came to in some kind of hut made of leaves. By the sounds I could hear I guessed that I was somewhere in the woods. A few seconds later, I realised that I was bound to something, and, while struggling to free myself, I became concious of a jiggling sensation. Looking down, I saw that I had somehow developed a large pair of man boobs and a belly that obscured most of my feet.
About an hour later, Brandon came in with a fat lady, followed by three fat people. It took me a few seconds to realised that the three people were fattenend versions of Lily, Marcus and Josie.
"What've you done to me Brandon?" I asked, angry.
"I've made you a werewolf of course" he replied "and every werewolf must have a mate, and since Marcus has Lily, you may have Josie". Josie looked pleased about this. "Now it is time for you to join us" said Brandon, removing my bonds. As soon as the last bonds were removed, I felt a terrible pain as my body changed into that of a werewolf's. Then hair grew all over me and I racked with pain as new bones developed and I grew a tail. After the transformation, I saw that the others had transformed too, and seemed to be beckoning me to come and hunt with them. The last thing I thought before my animal side overran my rational thinking was "I suppose it's a shame to stop being human, but some things must change".

Thank you to someguy for the idea of this story!