Two:
Casey thought she knew Derek. After years of living together, and, finally, dating, she thought she had him figured out. And then she met the guys.
Derek had always been careful about how much of his life Casey witnessed. Sure, he loved her more than life itself (on most days), but he knows how she can be and he didn't want to trouble her anymore than necessary. Particularly since most things he neglected to tell her would probably be over analyzed as reflecting negatively on her or their relationship. After three years of dating though, Derek was getting serious and, since he's not really a touchy feely, express yourself kind of guy, there was only one way he could think of to express how much Casey means to him and how much he wanted to wake up next to her every morning for the rest of their lives, no matter how difficult it [she] got.
So he called in a few favors with the managers of various Canadian and American hockey teams, cleared his schedule for the weekend, and, basically wore his heart on his sleeve for Casey to observe, analyze, reanalyze, and, hopefully not, crush.
A few days later, Derek and Casey were sitting at the bar of Toronto's Fairmont Royal York, waiting for her surprise. When the three of them arrived, Austin, Richard, and Jack, they were, at first, very cordial to Casey. After giving the expected man hugs to Derek, the three of them introduced themselves, and where they hailed from, and promptly, and politely, argued over who would buy her a drink.
Casey was, of course, flattered by the attention, and thought Derek could serve to learn a few pointers from those friends of his. It wasn't until after they left the bar and went out on the town, however, that her perspective of the guys changed, dramatically.
They were still polite, to her; but to Derek they quickly became, actually, just like him. It was as if being together suddenly transported them from their respective ages and back to age 16, where they were all nasty, crude, and annoying boys. Despite this, Casey, and Derek, after noticing that she wasn't scared away by his friends, had a good time that night and both found themselves looking forward to the next day.
When she awoke the next morning, however, Casey found herself outside her and Derek's apartment door, without a key. When she finally managed to uncover the long ago hidden spare from under the flower pot down the hall, she entered the apartment to find it looking apparently normal. Waking up outside was definitely odd, but, after seeing the apartment, she figured she just slept walked in the middle of the night. It didn't cross her mind that she and Derek shared the one-room apartment and, since he wasn't currently there, he must have left through the door, thereby passing her asleep outside it. She simply grabbed cereal out of the cupboard, made herself a much needed cup of coffee and, figuring Derek had left earlier to go out with the guys, sat down for some down time before the day began.
Derek, meanwhile, was sitting in the next door neighbor's apartment, nervously chewing at his fingernails as his buddies chortled over the chaos that was sure to ensue after Casey woke up and discovered their prank. The neighbor was out of town and had left a key with Casey and Derek so they could check up on the apartment every once in a while, and Derek's friends had convinced him to, in the middle of the night, switch the entire décor of his and Casey's bedroom with that of the next door neighbor. He gave in to his friends' crazy idea, hoping that Casey would be reminded of the good ol' days when he used to prank her, and not kick him out for his stupidity. Actually, at that moment, he was wishing that he had just stayed with the pranking and not gotten serious with her at all, thereby avoiding the entire situation all together. Unfortunately, he loved her and wouldn't have been content with that even if he'd tried.
Casey's relaxation lasted longer than expected, however, and Austin, Dick, and Jack all left, flying back to where ever they came from to practice for whatever hockey game they had coming up. In Derek's opinion, they were all cowards and left early because they didn't want to face Casey's wrath, but they assured him that, if they could stay, they wouldn't miss her reaction for the world. Despite his grating nerves, Derek agreed with them on that one.
After they left, Derek, fearing for his life, and valuing his relationship with Casey more than with the guys, attempted to quietly re-enter their apartment and switch back the two bedrooms to their original décor. A job easily completed by four well-muscled professional hockey players is not nearly as simple with only one professional hockey player, no matter how well-muscled. Unfortunately for Derek, this meant that Casey woke up from the nap that she had accidently taken after finishing her cereal and coffee, and caught him in the middle of recreating their bedroom's original look.
He quickly tried to chalk it off to redecorating, but Casey knows him better than he might think and she knew that he was up to something. She went into their bedroom and promptly had a freak out.
Derek attempted to calm her down with various excuses, but she refused to stop yelling at him until he told her exactly what happened to the bedroom. He told her about placing her out of the way as they moved belongings from one apartment's bedroom to the other, and, finally, leaving her out in the hallway without a key as a means of annoying her. Derek also told her that it was all his friends' idea, so she let him off easy and he only slept outside, in the hallway, for a few hours that night before she let him back in.
When the weekend began, Derek worried that his friends would push Casey away and cause her to realize that Derek was not really the man she thought. The night they left, however, after she took pity on him sitting forlornly out in the hall, and they snuggled up on the couch for a late night movie, when he asked her what she thought of his friends, her answer floored him and left him utterly speechless. While they were not what she expected, though they should have been, they did love Derek and, if they made him happy and supported him with their friendships, Casey figured she could put up with Derek's friends for however long Derek chose to put up with her.
Besides, friends like that made Casey realize how lucky she is to have a boyfriend like Derek. He respects her, loves her, takes care of her, and, if he trusts her enough to let her meet all of his friends, especially when she didn't think they could get much worse than Ralph, Derek obviously is much more serious about her than Casey even realized.
To Derek Venturi, Casey McDonald's easy acceptance of his friends, all of them, made her irresistible. Her love is his drug, and he's hooked.