A loud erratic pounding jolted Penny up in her bed. The sudden movement made her overbalance, fall off the bed and land hard on her hip. After a couple of seconds of swearing and surprise, She glared daggers in the direction of the front door before climbing to her feet with gritted teeth.

"I'm going to KILL you!" she yelled as she got closer. She grabbed the doorknob and jerked the door open. "What the hell do you want, Sheldon?!"

He glared down at her with equal fierceness. "You are wrong!" he hissed.

Penny was taken aback by the anger in her whack-a-doodle's voice. "What? Sheldon it's 3 am! You know better than to wake me up!"

Sheldon pushed into the apartment, dragging a whiteboard behind him. He propped it up on her couch and reached around her to slam the door shut. Penny gasped as she looked up into his face. "Three years, Penny. You have wasted three years for us both!"

"What on earth are you talking about?" she asked warily.

Sheldon gripped her upper left arm and moved her toward the couch. "Look. Read it! See what I see!"

Penny focused on the whiteboard. At first none of it made any sense to her. It was divided into four sections. She stopped taking in the whole board and focused on one section at a time. She ignored the equations, knowing she would never figure those out. Instead she read the things written beneath them.

Take care of each other when ill.

Sing Soft Kitty.

First person the other turns to for advice or help.

Polar opposites in behavior and interests, yet always manage to find common ground.

Even during a prank war we maintain a level of comfort with each other.

Neither of us is happy when the other is upset.

She moved on the next block.

First attempt at a relationship ended badly, almost removing her from the group.

Sexual congress is most often impossible without copious amounts of alcohol.

Trust is absent from relationship.

Neither betters the other. They instead tend to stagnate or even move backwards.

She swallowed hard and moved to the next section.

Relationship is uncomfortable and uneven.

Physical attraction is absent. One party is desperate for affection, trying to force it where none exists.

Other party has a fondness for first party, but affection and attraction belong to a third.

Neither betters the other. The entire relationship is a balancing act. One pushes and the other retreats.

Penny's heart skipped a beat as she moved on to the fourth and final section.

Occam's Razor states that among competing hypotheses, the one with the fewest assumptions should be selected.

Amy is desperate for love. She has spent her life alone and immediately clung to the first people to show an interest in her personally. She has confused friendship for love.

Leonard does not love Penny, as evidenced by the frequent times he has chased other women. He simply enjoys the close proximity of a beautiful woman, and the status of having a "hot chick". Leonard desires to be loved and needed above all else.

Penny allowed herself to become involved with Leonard because of fear. Fear of being alone, fear that she could not have true love, fear that I would not love her. She settled for Leonard because she did not think she could have me.

I enjoy Amy's company when it comes to intellectual endeavors. I enjoy Penny's presence in all aspects of my life, even when we argue. I entered into a relationship with Amy because Penny thought I should, and I respect her opinion above all others.

Penny and I should be together because we love each other. Leonard and Amy should be together because they fill each other's needs.

Penny closed her eyes, and took a few deep breaths. The things she had read swirled around her head like a tornado. Surely she was dreaming, right? A gasp caught in her throat as Sheldon's lips settled on hers firmly. After a few breathless heartbeats he pulled away and she opened her eyes.

"You are wrong," he said softly. "I'm The Guy."

"You know they will be angry, right?" she asked worriedly.

"You know I have never cared for the opinions of others," he answered.

"Are we really doing this?" she asked hopefully.

"There is only one solution, Penny. Will you be mine?" he asked just as hopefully.

"Yes," she breathed.

"Then we are doing this," he told her.

And they did.