Hello again readers! So it's been ages since my last Chipmunks fanfic… I've jumped ship and eventually made my way back. Now with a little help from my writing buddy Kuro Raka Shimo, we've decided to come up with something for my page. And it was time to finally venture into the M department.

Hope you like it, and as the summary suggests, you'll be seeing more sexually related stuff in the future chapters. Enjoy!

Chapter 1

Nighttime at the Seville home. Dave was fast asleep in his room, while the three chipmunks were safely nestled away in their beds. The full moon and stars above shone gently through the window, offering their soft lights to the slumbering world below.

However, the moon's light brought out another thing. Theodore stirred in his bed, grumbling to himself as he slowly woke up. He blinked the sleep from his eyes before gasping.

The light of a full moon…

Theodore rolled out from bed, eyes darting nervously around the room. Thankfully, his brothers were still snoozing. He adjusted his onesie pajamas before going over to their window. Careful not to wake anyone, the little chipmunk opened the latch and leapt out, landing evenly on a tree branch. He scaled down the tree in their backyard, grunting lowly as he landed on his feet.

Gazing back up at the window, Theo let out a little whine - if only he could let his brothers in on what he was about to do...

But eventually, he turned away and ran off.

Alvin's eyes bolted open. The moment Theodore was gone, he leapt out of bed. That little butterball had been acting weird ever since the whole werewolf incident was solved. And yet, he still snuck out some nights… Alvin had been keeping a close eye on his baby brother for the past month or two.

What's up with Theo? Gee, I hope he's alright…

The more Alvin thought about it, his curiosity wouldn't leave him alone. He had no choice but to give chase now. Grabbing a flashlight from his nightstand, Alvin was out the window in no time, looking around before following after the light sound of footsteps.

The streets around the neighbourhood were empty, as could be expected in the middle of the night. Not even a stray cat prowled around the alleys. Alvin kept his back up against every possible corner or wall he could find, before making sure the coast was clear to continue walking. Pretty soon, he had Theodore in his sights.

They were going towards… the school? Alvin stayed on the sidewalk, careful not to let the flashlight give himself away.

He could have sworn he saw Theodore walking along the pavement, before turning a bend. One second his baby brother was there, and the next…

Alvin was staring at an empty sidewalk. There was no sign of Theodore anywhere.

"Theo?" Alvin whispered, shining the flashlight around. "Theo, where are you?" No answer.

"Oh man, what am I gonna tell Dave? No, forget that - he's so going to ground me for life if I don't find him! Theooo?" Alvin's eyes darted about as he searched frantically for his little brother. "C'mon man, where are you? We gotta get back home!"

He tensed up, fur standing on end as he heard a skittering behind himself. He turned around, only to see a few leaves blowing in the breeze. Eyes wide, Alvin scolded himself internally as he tried regaining his composure.

"Face it, Alvin, you're only being a scaredy cat. There's nothing out here that will harm you. No such things as -"

"Alvin?"

Something tapped him on the back.

"AAAAHHHHHHH!" The high-pitched scream from Alvin could have woken up the entire neighbourhood. He whipped around, flashlight raised and glowing. "Back off! I'm armed!"

Unfortunately for him, the light landed on a familiar sight. Theodore stood in front of him, and from the look on his face, he was trying not to burst from his brother's squeal.

"What the- Theodore! What the heck, man? What're you doing out here scaring me?! Geeez..." Alvin squeaked out, a paw raised to hold his chest. "Do you have any idea how much trouble we'd get in if Dave found out about this?"

Theodore snickered, then burst out laughing, holding on to his belly as he doubled over. "Hehehe… oh, oh my gosh, I'm s-sorry!" He laughed, rubbing his eyes as he straightened himself out, sighing in relief.

Alvin growled, blushing in embarrassment as he crossed his arms over his chest. "Yeah yeah, laugh it up. But don't expect me to cover for you when Dave hears you've been sneaking out!"

"Hoo… Okay, okay, I'm good." Theodore huffed, standing up straight and taking a deep breath. "Anyway… I have a reason to be out here. You didn't have to follow, you know." He spoke, adjusting the zipper on his pajamas as he continued on his path. "Sure was a good idea to scare you though~"

"Shush! You still have some explaining to do!" Alvin said, following him. "What are you doing out here in the middle of the night, anyway? You're not sleepwalking by any chance… are you?" He put out a hand and waved it in front of Theodore's face.

Theo giggled. "You're being silly, Alvin. Come on, let's go!"

The rest of the walk was spent mostly in silence as Alvin lingered behind Theodore. He couldn't help noticing the subtle changes though, no matter how much he denied them. Whenever a hint of thought came, Alvin just shook it away in disbelief.

After all, it had been too long since everything was fixed.

But the way Theo's fur seemed to grow and darken… his steady crouching down until he was practically on all fours… And unless Alvin was mistaken, his brother's ears had grown into sharper points.

Soon enough, they were at the school's playground. Before he could even ask, Theodore was bolting off, heading for the merry-go-round. Alvin made sure to distance himself, but kept an eye on Theodore. If things weren't all better…

"Hey Alvin! You gonna join me or just stand there?" Alvin blinked a few times, his vision focusing on Theodore, or trying to, as he spun. It was like watching a mini tornado on the loose.

"Uh, hey, Theodore?" Alvin approached him slowly, keeping the flashlight on his brother. "Theo? Are you… feeling alright?"

"Grrr… huh? Oh, yeah, I am!" Theodore answered as soon as the ride slowed down. Alvin got a good look at Theo's face. He winced.

There was no denying the two fangs sprouting from Theodore's lower jaw, or the mane of fur growing around his face. Even the way he behaved was… familiarly canine.

"Theo… there's something I need you to do for me." Alvin started.

"Can it wait? I gotta burn out all this energy!" Once Theodore got off the ride, he started to run about on all fours, this time in circles as he chased the bushy wolf-like tail that had sprouted behind him.

"Er… Sure?" There was nothing much Alvin could do but wait until Theodore had tired himself a little. At least he could keep an eye out so nobody would see them in the park at such odd hours.

"So, you're still a werewolf, Teddy? I thought everything went back to normal after you bit Mister Talbot?"

"Wha-oh yeah! Raf! I thought so too!" It seemed as though Theodore was hardly ever going to run out of steam. When at last he stopped chasing himself, he hardly broke a sweat, although he panted eagerly like a dog would. "I guess it just… put everything under control? I don't get a whole lot of urges or anything anymore."

"Does that mean you won't go around biting anybody you see?" asked Alvin.

"Nope!"

Alvin looked a little disappointed. "But… What if I wanted you to?"

"Hmm?" Theodore tilted his head, giving his ears a scratch with his foot. "You… want me to bite you?"

"Well, yeah! I mean, even when you were out of control, the whole werewolf thing was kinda cool!" Alvin said with an eager tone in his voice. "Just think of it! You get to run and howl at the moon and be stronger! Heck, we don't even have to go to sleep! How awesome is that?"

Theodore paused, ears wiggling a bit at the thought. He shook his head, however, waving his paw. "No way, Alvin. You think it was fun at first? It was all scary! Sometimes I thought I would hurt you guys!"

"Aw come on, Theo? Pretty please? Give me a teensy nibble?" Alvin looked at Theo with big pleading eyes.

"I'm sorry, Alvin. I just don't want us to get into trouble..." Theo said, moving towards the swing set. "It's better if you just stay the way you are."

Hearing this made Alvin pout, planting his paws on his hips. "Oh yeah, what's that supposed to mean? You saying I'll just be trouble? Oh… I know." Alvin crossed his arms, turning away from his brother. "You think I can't handle it!"

"W-what? That's not it!" Theodore protested. His words fell on deaf ears as Alvin pranced around.

"Oh, look at me! I'm Theodore, and I'm a goody-good two shoes! I think my big, strong big brother can't handle being a werew- Yeowch!" Alvin yelped out, leaping off the ground and grabbing his rear. "Theodore… you bit me! Geez!"

Theo was down on all fours, growling lowly at him. "Don't make fun of me, Alvin! I said I… wait… you tricked me! Alvin, how could you?!"

Alvin laughed, tugging off his pajama pants to look at his butt, eyeing the two fresh bite marks that punctured through his boxers. "Hehe, we'll see who can't handle it sooner or later, huh Teddy boy~?" Alvin taunted, wiggling his rump tauntingly in his brother's face.

Growling, Theodore crossed his arms over his chest. A passing cloud caused his form to waver a little. "Hmph. Fine, Alvin. Go ahead. But don't come whining to me when you can't keep control!" He said, giving Alvin a light shove as he stomped past him.

"Oh relax, will ya?" Alvin called, watching as his little brother headed out of the playground on all fours. "Hey! You couldn't just keep this hidden, Theo! Someone was gonna find out eventually!" His words got no response. Once Theodore was out of his sights, Alvin gulped, looking up at the sky.

The full moon's glow seemed more like a scowl now…. And the strange tingling coming from his rear filled him with worry instead of the excitement he expected.

"Uh… Theo?" Alvin called, before cursing under his breath. "Great move, Seville. Great move. You really did it this time." He started to make the long walk home, already feeling a little light-headed.

"Boy, what a night..."

By the time Alvin climbed back up the window and reached his bed, his head was spinning. The room looked a little blurry, but he could make out Simon's figure, still fast asleep. Only Theo was nowhere to be found.

"Probably the little butterball's still sulking… I hope he makes it back okay... "

Or what if he was out on a nightly hunt? The thought of joining his baby brother, being able to run about on all fours at top speed made Alvin's heart beat a little faster.

Maybe a little too fast… Alvin felt short on breath once more. He pulled down his pants again, turning his head around to inspect. This time, the bite marks seemed to have a slight pinkish glow to them… They looked almost like two crescent moons glowing on his butt.

"Weird… Grrr…" Alvin put a hand to his mouth, but there was no mistaking the rumbling growl that came from within. He staggered over to his bedpost, gripping it hard as his head grew heavy, spinning again.

"Gonna… sleep it off, grrrr…"

His world went black even before his head hit the pillow.

To Be Continued...