I'm doing two holidays with this chapter. I'm sure you don't mind, right? ;)
Santa's List Day (December 4th)
Sheldon and Leonard were in the middle of 3-D chess when there was a knock on the door. Sheldon glared at the game and remained seated. Leonard rolled his eyes and stood to answer it. "You keep this up and you're going to make Penny mad," he mumbled.
Sheldon ignored him and just glared harder as he raised his hands toward his head. Leonard opened the door with a smile. "Hey, Mark. Come on in. Penny called and said she's on her way. She got held up in traffic."
Mark nodded and walked into the apartment. "I thought she might. Rick called to tell me there was a wreck on Union and that Penny might be late getting home from work." He gazed at the man determined to explode his mind and sighed. "Hello, Sheldon. Still hate me, I see."
Sheldon gave up with a supercilious expression. "On the contrary. I do not hate you. I just don't trust you."
Mark grinned, just to irritate the high strung scientist. "Afraid I'll snatch Penny away?"
Sheldon stood abruptly. "Highly improbable. Penny chose me, in case you forgot."
Mark shook his head with a smile and sat down on a kitchen chair. "Relax, big guy. I care about her, as a friend. You don't have to worry about me. I'm just glad she's happy."
The door opened and Penny stopped just inside the door. She immediately noticed the hostile position Sheldon was in and rolled her eyes. "Holy crap on a cracker. If you two are beating your chests I'm going to lock you both in the closet until you learn to get along."
A brunette appeared behind Penny and looked around the room curiously. "Who's beating their chest?"
Leonard smiled and walked over. "Hey, Missy. Sheldon and Mark are. What brings you to Pasadena?"
Missy hugged Leonard briefly and looked at her brother before turning to the stranger. Her eyes widened slightly. "Oh, umm, Mommy wanted me to see how Shelly was doing since I was heading to Burbank to see an old girlfriend."
Penny looked carefully between Missy, who was looking a bit stunned and Mark who was looking very stunned. Slowly she smiled and looked at Sheldon who was frowning with confusion. "Missy, this is Mark. He's a very dear friend and the partner of the man I now work for. Mark, this is Missy, Sheldon's sister. She's going to be staying here for a couple of days."
Mark walked over and held out his hand. "It's a pleasure to meet you," he said softly.
Missy smiled at him, blushing lightly. "Hi."
Penny walked over and gave Sheldon a kiss. "Okay, I'll be back as soon as our time slot at the mall is over. Amy and Bernadette are probably anxious for us to relieve them." Penny walked toward Missy and Mark and sent Leonard a wink. He shook his head with a smile, instinctively knowing what she was about to do.
"Missy, Mark and I are manning a booth at the mall where kids can write letters to Santa. Want to join us? It's a lot of fun." Missy nodded, not taking her eyes off Mark. He grinned widely and held out his arm. Missy slipped hers into his and they headed down the stairs. Penny laughed lightly and followed them out.
Sheldon looked at Leonard once he door was closed. "What just happened?" he asked.
Leonard clapped Sheldon on the back. "Looks like you might be getting a brother-in-law. Especially if Penny has anything to do with it."
Sheldon jerked back and turned to the door. "No!"
Christmas Eve (December 24th)
The bathroom door opened and Sheldon glared at Penny. She smirked and continued to apply her makeup. Sheldon closed the door and crossed his arms. "This is not acceptable, Penny."
She dusted on a little blush and looked at him in the mirror. "Sweetie, it's not your decision."
Sheldon huffed. "It's not yours either, yet you seem to be doing your best to affect the outcome."
Penny giggled and turned to face him. "Sheldon, you don't like Mark. I get it. But Missy does. And he likes her. They are both grown ups. This isn't the 1700's. You can't just banish Mark from the kingdom and lock your sister in a chastity belt. She flew all the way back out here to see him."
"I don't see why not," he muttered petulantly. "He's too old for her. And they live too far apart. And he seduced her!"
Penny shook her head. "They're adults, Sheldon. They've slept together. So what? Leave them be."
The bathroom door flew open and Missy stormed in. "Sheldon Lee Cooper! Where is it?"
Sheldon blushed slightly and looked away. "I have no idea what you are talking about." Penny and Missy watched his left eye twitch madly. Both women crossed their arms and waited.
"What did he do?" Penny asked wearily.
Missy pointed at him angrily. "Before I left home yesterday, I went and bought a present for Mark. He hid it!"
Penny raised an eyebrow and spoke calmly. "In that case, I'll just give you the one I bought for him as a replacement for the one he took. I'm sure Mark will love it. Especially once you tell him it was originally Sheldon's gift."
Sheldon gasped and looked horrified. "You can't! That's MY gift!"
Missy crossed her arms. "And what do I give Mark?"
"His walking papers?" suggested Sheldon angrily. The women watched him silently for several long seconds. Finally Sheldon huffed and stormed out into the living room. He reached into the Batman cookie jar and pulled out the gaily wrapped box. He held it out to Missy and then stomped over to slump in his spot.
Penny walked over and sat beside him. She wrapped her arms around his neck and kissed him softly. "Sheldon, please, for me? Can't you at least try to get along tonight? After all, it's all because of Mark that we're together. You don't have to be his friend, but can't you at least find a way to be civil?"
Sheldon looked at his girlfriend with startled eyes. Slowly his expression softened. "You know I once said almost the same thing to Amy about you." He sighed and looked at his hopeful sister. "Okay. I will attempt to be civil." He looked back at Penny. "For you."
Penny smiled and hugged his tightly. "Thank you, sweetie."
Sheldon hugged her back. "The things I do for you," he lamented in her ear.
Penny smiled against his neck. "I love you, too."