Here's 4! I wanted to make y'all wait for the chapters, but I'm so anxious to get it out of my system already. Like I said, I've had it written for a while now! Ch. 5 is in the works, but I have like 2/3 of it done.

Also, Happy Birthday to Michael Seater! :)

Enjoy!

Derek started slowly. First he would stop pranking her, which she didn't mind at all. Casey just figured he was exhausted from practice was all, so she didn't bother bringing it up. He'd probably start again once she mentioned anything. He then started being polite and doing all the chores in the house that she would normally do. Say, like wash dishes when she cooked, throw out the trash, sweep the floor. Little things like that. Casey had no complaints! He was actually good at it, why would she?

It was when he started offering gentle smiles when she would crack one of her lame jokes that Casey was getting freaked out. He would usually roll his eyes and purposely bump into her to make her stop talking. Honestly, the smiles were encouraging it. She obviously knew something was up, but refused to bring it up, partly because she enjoyed the special treatment so much. Special treatment from Derek was more than she could ever imagine from him. She felt as if she must be doing something right.

Derek realized that being nice to Casey wasn't so hard at all; it was actually as easy as breathing. He'd spent so much time disliking her that he never realized all the good aspects about Casey. Like the fact that she was a great cook, she was brilliant with keeping a conversation going, and she actually had a really nice smile. It creeped him out how much he was actually enjoying the idea of possibly sleeping with her. He still knew it would be a challenge getting her in bed. Before he'd taken the time to be nice to her, he'd be disgusted with the idea of sleeping in the same bed together, let alone actually performing these kind of activities in it, but with careful observation, Casey McDonald was just the type of girl he'd bring home to meet the parents…you know, if they didn't share parents. He never saw her as a step-sister, let alone a sister, though. She was more like an acquaintance that he got stuck with for life. A very attractive one at that.

The weird part about getting to know Casey was that he already knew everything about her. He knew her favorite colors, bands, what made her tick, what made her smile, her favorite artist, favorite poet, what she cares about the most, the amount of guys she's dated in her lifetime, size bra, size panties, size pants/shirts/shorts/shoes, and lastly, he knew just how predictable she was and just how unpredictable she can be. Casey McDonald wasn't so complex, but at the same time was the hardest puzzle he'd ever have to deal with.

"So, Casey…" the day finally came when Derek decided he may as well get it over with and ask her out.

"So, Derek…" she teased, turning the page in her text book, not looking at him. They were in the living room, and Casey was on the floor between the couch and the coffee table doing homework with the television on low volume.

"You wanna like…go to a movie or whatever on Friday?" he sat on his recliner nonchalantly and turned up the volume on the TV. Casey's head snapped up and she looked at him suspiciously.

"With you?"

"Yes, with me, why else would I be asking?" he rolled his eyes, landing them on her face. She looked dumbfounded, honestly.

"I'm just confused, you never try to hang-out with me outside of the apartment or family dinners…what's the catch?" she leaned against her elbow with her chin in the palm of her hand, and studied his face. She can catch a lie from Derek anywhere.

"You know…just wanna spend time with you."

"Why?" she sighed, running her hand through her hair. Derek leaned his head back, and groaned.

"Can't you just say yes or no?"

"Are you paying?"

"If I say yes, will there be more questions?" he looked at her. This was way more difficult than asking any other girl out. He'd known this girl for almost five years now and was never allowed to turn his charm on for her, it was weird starting now.

"So you're paying?" she smiled.

"Yes, okay?!"

Casey only smiled as a blush ran against her cheeks. "Are you asking me on a date, Derek Venturi?" she asked shyly.

"I'll probably take it back if you keep acting so girly!"

She giggled, and looked down. This reaction gave Derek a weird feeling in his stomach. Was he actually pleased that she seemed so endeared by him asking her out? Oh, God, this wasn't good…

"Well, the answer is yes." She grinned, and stood up.

"Really?" he didn't know if she was pranking him back or something. Casey collected her books and stood next to him.

"I said yes, didn't I? I've honestly wondered why it's taken you so long to finally ask." She shook her head, and shifted her books to her hip and looked down at him with half a smile.

"You expected this?" his eyebrows rose. He thought he'd been pretty nonchalant around her.

"Well, you have been especially nice to me lately. You've also been pretty good about cleaning up and studying for your classes around me." She shrugged. "I figured you were buttering me up for something."

Derek didn't know what to say. She was being too cool about this, and was just waiting for that Casey freak out that was always on the edge of any given situation that would possibly be out of her plans.

"You're not gonna freak out that you're going on a date with your step-brother?" he was watching her, wanting to mentally note the exact moment that this all clicked in her head.

She just sighed, frustrated with his questions. "I've obviously thought this through, Der. Even before we started university." She blushed a little at that last sentence.

"Before university?" Derek was slightly amused. Such a bold confession from Casey. Goody-two-shoes Casey McDonald has thought about dating her step brother.

"Oh, don't act so surprised, Derek!" she laughed out, and sat on the arm of couch beside his recliner, placing her books in her laps. "We were fifteen when we first met, don't you think I've even debated the possibilities? I mean, yeah it would be weird telling the folks and the sibs, but I think they'd have to live with it. We are adults, after all."

He had to admit she had a point. Of course he thought about it a lot when they'd first met, but never really acted upon it. They were supposed to be siblings for Christ's sakes! Of course it was impossible for either to see each other in that way and decided that it was more like they were roommates living together and having to acknowledge one another for the rest of their lives.

"Okay, okay, you got me." He grinned at her. "Since when did you become the rational one?"

Casey only shook her head and smiled. She looked down at the books in her laps, and shrugged. "It's just a date, anyways. It's not like you're actually my boyfriend."

"What if I wanted to be?" he blurted out without thinking about it. Where did that come from?

There was a long silence after that, the two just looking at each other. He didn't know what to say. He was honestly a little embarrassed about his silly little question, and broke the gaze first, surprising Casey.

"Well, we'll see how you do on the first date, yeah?" she laughed a little, and stood up again.

Derek managed a smile, and shrugged, "You won't be able to stay away." He winked at her, and a giggle erupted from her chest, and she covered her mouth.

She walked towards the hallway to her room. "I'm not just another girl, Der. Remember that. There's more to me than tits and an ass." And she was in her room.

His mouth hung low, mostly because Casey said tits and ass. He sort of wanted to laugh. If she'd only known what he was up to. She'd have messed him up so badly, they would have her arrested, and he'd never be able to walk again. Though, he was quite satisfied that it was so easy to get her to say yes. He was obviously doing something right, and he liked being nice to her. Not that he'd completely stopped teasing her, though. They weren't Casey and Derek without the friendly banter.

He got a funny feeling in his stomach thinking about Casey genuinely wanting to spend a Friday night with him. It even made him involuntarily smile. He didn't even realize he was smiling until he felt sore from his cheeks. He can only shrug this reaction off. He was just happy to be winning the bet so far.

Right?