Penny blearily wandered into the boy's apartment in search of coffee, running into a whiteboard the second she opened the door.

"What the hell?" She managed to catch herself before she hit the floor and blinked in confusion, staring at the total destruction that surrounded her. The usually immaculate apartment was cluttered with old coffee cups, whiteboards, and crumpled bits of paper.

Sheldon rushed over, a cup of coffee in his hand. He thrust it at her distractedly, rescuing the whiteboard she had nearly knocked over.

Penny eyed the cup momentarily before shrugging and downing the coffee quickly. It was probably Sheldon's, but by the look in his eyes she would need the extra caffeine.

"Sweetie, what's wrong?"

He glared at the incoherent scribbles on the various whiteboards. "It appears that I am stuck."

Penny quickly grabbed another cup of coffee from the coffee maker. "Uh oh. Um…is there anything I can do to help? Or, um, should I call… Leonard? Or someone?"

His eyes lit up as he fixed his gaze suddenly on her. She took an instinctive step backwards as he sent her his best creepy-Joker-grin. "Actually, you could help me with this. I am endeavoring to retaliate against the series of so called 'practical' jokes that Howard, Leonard, and Raj have been engaging in against me."

Penny grinned. "OOOOh,yes! You definitely need my help." She eyed the whiteboards with new interest. "You are getting bogged down on the technical details."

Sheldon squeaked as she deftly snatched the marker out of his hand and erased the closest white board.

"Now if you really want to screw with their heads, you need to give depth to their darkest fears…"

Two weeks later, the night of the University Halloween function, their plan began. Penny and Sheldon stood in the hallway, putting the finishing touches on their costumes.

Penny spun, modeling her full pink skirt and jeans jacket. She was dressed in what Sheldon had assured her was a screen accurate replica of Rose Tyler's costume in the Idiot's Lantern. The pink helmet swung jauntily from her wrist.

Sheldon really did look handsome in his suit, the brown and blue pinstripes showing off his lanky form. And his hair, while not the same as David Tennant's gravity defying mess, was a fair approximation.

"Ok, last chance. Are you sure you are comfortable with this plan?" Penny raised a challenging eyebrow. She had been waiting for him to back out of this since she had suggested it, and was impressed with how determined he had been to follow through with their caper.

Sheldon nodded confidently. "I will be in character, Penny. Although I do not usually engage in unsanitary activities such as hand holding and touching, David Tennant's portrayal of the Doctor is quite-" He stopped abruptly as Penny reached her hand out for his and he automatically recoiled.

"And you are certain you are not sick?" Sheldon queried to mask his hesitation.

Penny sighed. "One hundred percent. Please don't take my temperature again."

Sheldon took a deep breath and then grabbed her hand. "Excellent!" He gave her an only-slightly-manic smile. "Let's go emotionally scar my friends!"

Penny had to admit, she had never seen this side of Sheldon before. He had thrown himself whole heartedly into their ruse- although, now that she thought about it, he never really did anything half way. He had been holding her hand for almost…she checked her phone… two minutes, and although he was still sweating slightly more than usual he had actually relaxed his hand to the point where she could feel her fingers again.

She smiled proudly at him. "The boys are going to flip."

Sheldon laughed his weird breathy laugh. "Yes, this is going to skew their entire worldview and rip them out of their comfort zones, possibly forever."

Penny laughed. "Sometimes I worry about you, you know. Not now, but sometimes. You ready?"

Sheldon nodded, his grip on her hand tightening again to the point of almost pain. She winced and ran a hand down his arm in a soothing gesture. "You can do this sweetie, I promise. Anyone as smart as you can do anything you set your mind to, yeah?"

He relaxed. "Oh, of course. I was merely allowing my nerves to negatively impact me for a moment. You are right, this will be simple. Ready for the best bazinga ever?"

Sharing a conspiratorial smile, they walked indoors.