Penny entered Leonard and Sheldon's apartment as if it was her own, then she curtsied. She was expecting applause, so she looked up to see Sheldon staring at her from the kitchen bench. Penny looked around but Leonard, Howard and Raj, the people she was expecting to applaud for her, weren't anywhere.

"They went to get the take out," Sheldon responded before she could ask. After he said it, Penny's face turned into a childish pout, Sheldon thinks that's what it looks like, so he rolled his eyes and said,

"Don't worry, they'll be back soon to feed your ego," he put on a fake smile.

"My ego is not as big as yours Sheldon," Penny snapped back at him casually, as if this was a normal conversation.

Sheldon handed her a glass of water, then responded, "at least I have reasons for my ego. I am gifted and talented."

Penny stopped the conversation visage and half yelled, "Heeey! What's that supposed to mean!?!" Penny knew it was a cross-line, a 'don't go there' question. But of course Sheldon didn't catch her tone, so he said,

"Obviously it means you are not talented, for example in the play you just performed in."

"Hey, just so you know, I worked hard to get into Avenue Q." Penny yelled.

"Exactly, Penny. I must point out, that you didn't need to act. Plus acting is a silly career choice, people who enter that occupation, only see them for what others see them as," Sheldon calmly retorted.

"I do acting because I love doing it. Hey, I don't need to justify myself for you. I'm leaving."

"Did I cross a line, Penny?" Sheldon didn't know what reaction he would get from her, when he said those things.

"Oh yes, a big line Sheldon! You have hurt me by insulting the things I love."

"I don't understand that feeling."

Penny had the door open to leave, "Mark my words, Dr. Sheldon Cooper; you will understand the hurt, when I take the things you love!" She slammed the door behind her.

She stomped over to her apartment, furious, when Leonard came up the stairs with Howard and Raj.

"Aren't you coming over to our apartment, to celebrate your wonderful performance Penny?" Leonard asked. But Penny gave them a cold stare, and then slammed the door in their faces.

"What's up with Penny?" Raj asked.

"I bet someone knows," Howard responded.

Leonard opened the door to his apartment; the three of them looked through the door to see what Sheldon was doing. Sheldon was sitting at his desk chair, thinking.

Then Sheldon said out loud, "'Things that I love'" then he laughed, in the way he laughs, and said, "The list should be small."

Sheldon smiled and said, "Plus she won't be able to get me back until I come back, because I am going on a train to San Francisco, tomorrow."

Leonard, Howard and Raj didn't want to get involved with Sheldon and Penny's fights, so they didn't ask. They just have to wait, until it blows over.