This story starts right after Penny kisses Leonard during the Halloween party in season 1. The part in italics at the beginning is from the episode.

Penny: God, what is wrong with me?
Leonard: Nothing, you're perfect.
Penny: Gosh, I'm not perfect.
Leonard: Yes you are.
Penny: You really think so, don't you?
Leonard: Penny?
Penny: Yeah.
Leonard: How much have you had to drink tonight?
Penny: Just... a lot.
Leonard: Are you sure that your being drunk, and your being angry with Kurt doesn't have something to do with what's going on here?
Penny: It might. Boy, you're really smart.
Leonard: Yeah, I'm a frickin' genius.
Penny: Leonard, you are so great. Why can't all guys be like you?
Leonard: Because if all guys were like me, the human race couldn't survive.

Penny looked at her hands in her lap, "I should go back to my apartment and tell everyone the party's over."

"Do you want help cleaning up? If you make Kurt leave, I have no problem helping," offered Leonard, watching Penny stand from the couch and approach the door.

"No," she turned around in the doorway, "I'm just going to crash once they're all gone. I'll deal with the mess tomorrow."

Stopping her from exiting his apartment, he spoke again, "Do you think we could talk about what happened here? In the morning, once you've sobered up?"

"I have to work the lunch shift. It was just a kiss and I'm drunk. I don't think we need to talk about it," Penny brushed off his request before continuing to exit the apartment, turning back one more time. "I'll see you later. Good night, Leonard."

Rolling over the next morning, Penny snuggled against the warm body next to her, bolting upright when the man spoke, "Morning. Last night was great. I'm glad you reconsidered after we talked."

"Oh, god," Penny put her hands over her face.

The man grinned, "You said that a few times last night. Best Halloween party I've ever been to."

"You need to leave. I need to clean up and get to work," Penny was already scrambling toward the bathroom to take a shower.

"So, you want to do this again?"

Penny turned on her heel in the doorway of the bathroom, "I don't know. Can you please just leave so I can get ready for work?"

Three weeks later

Howard quickly grabbed the door to the lobby of the apartment building, glad to see the blonde who held the door after he called to her as he approached. "Penny, I'm glad I ran into you. My mom hosts Thanksgiving every year. She told me to invite you if you're not going home for the holiday."

"I don't know," sighed Penny, trudging up the stairs next to the engineer. "I might have to work that day."

"You've been working a lot lately; we've barely seen you since your Halloween party. I know for a fact that The Cheesecake Factory is closed on Thanksgiving. You won't be working that day. Please, my mother said she wants to meet the woman who chooses to hang out with us all the time. She thinks we've made you up."

Reaching the fourth-floor landing, Penny sighed again outside the door to her apartment, "Fine. What time do I need to be there?"

"Dinner is at five. Feel free to show up whenever. We watch the parade before watching Star Wars while my mom cooks, but I could try convincing the guys to turn on a football game if you wanted," offered Howard, reaching for the doorknob of apartment 4A.

"Thanks. I suppose I could help your mother cook so I don't have to listen to Sheldon complain about him not being able to watch Star Wars. Although, Star Wars isn't usually a Thanksgiving movie. Why do you guys watch it?"

Howard stopped as he opened the door, "It's that or football and we aren't watching football. Aren't you joining us for dinner tonight? It's pizza night. You haven't joined us in weeks."

"Uh, I don't think so. I'm pretty tired from work. I think I'm going to put on my pajamas and go to bed early."

"Okay. Have a good night, I guess. I'll text you my address for Thursday," Howard watched as Penny entered her apartment and closed the door behind herself. Making his way into apartment 4A, he greeted his friends, "Penny's joining us for Thanksgiving. My mother insisted I invite her."

Groaning, Raj complained, "Now I won't be able to say what I'm thankful for when we go around the table. You know I can't talk in front of women."

"You've always had to whisper your answer when Mrs. Wolowitz is there," Sheldon reminded the astrophysicist. "Nothing will be different, aside from there being one more place set at the table."

Leonard looked at his roommate in disbelief, "Who are you and what have you done with Sheldon?" When Sheldon narrowed his eyes, questioning the shorter man, Leonard explained, "That is not the reaction I'd normally expect from you when we tell you something is being done differently than in past years."

Sheldon shrugged his shoulders, "I don't really care about Thanksgiving, but I know some people, people like Penny do. She might as well join us for a traditional Thanksgiving meal since she's being invited."

"Is everything alright? You were pretty quiet during dinner. From what Howard has told me about you, you're not the quiet type," Mrs. Wolowitz asked Penny after the blonde volunteered to help with the dishes following Thanksgiving dinner.

Penny shrugged, "Yeah, I guess. I've been working a lot of hours the past few weeks. I really want to go home for Christmas and that can't happen if things don't start to pick up at the restaurant."

Placing a container of leftovers in the refrigerator, Mrs. Wolowitz crossed the kitchen to where Penny was placing the plates in the dishwasher. Patting Penny on the back, she spoke, "The holidays can be hard when you're away from your family. That's why I invite Howie's friends over whenever I can. Now, we don't celebrate Christmas in the traditional sense since we're Jewish, but we have created a few traditions over the years for what we do on that day. I make cinnamon rolls for breakfast, giant ones that are practically the size of your head. We order Chinese and watch National Lampoon's Christmas Vacation. It's the only Christmas movie I have to watch every year. You're more than welcome to join us if you'd like."

"That sounds nice and I've enjoyed spending the day with you today, but I'm not sure right now. Can I let you know when it gets closer and I know if I'll be able to swing going home?" Penny hesitantly asked.

"Sure," Mrs. Wolowitz replied. "It's tough being an independent young woman, but don't push your friends away in the process. You never know when you'll need to rely on them and you don't want it to seem like you're only around when you need something. If you ever need to talk, woman to woman, I'm here."

Smiling, Penny thanked the woman, "I appreciate that. Thank you."