A/N:Hello! This is my 2nd Doctor Who crossover. But my first Flash crossover. This story takes place pre-particle accelerator. So the Doctor helps S.T.A.R. Laboratories build the particle accelerator. The summary should have explained it. Please review! I love reviews. And if you would like me to write short one-shot stories, I will. Just review. And read my Doctor Who & Maleficent crossover. I will try to update both stories every Wednesday. (very long author's note) Thanks for reading my story.

The Doctor was sitting in the T.A.R.D.I.S library reading a history book on the early 21st century for a quick re-cap to see if he missed anything. The Doctor was near the end of his 11th life, (12th if you count mister grouchy pants during the war). He was going through 2005 in the book when he noticed something odd. He was on page 1,247 of the book. On the top it said "Dr. Well's: Creator of S.T.A.R Laboratories Particle Accelerator" The Doctor looked at it questionably before he got out of his chair and walked quickly to the T.A.R.D.I.S control room with the book in hand.

When he reached the console, he slammed the book down on it and flipped a blue switch, turning on the T.A.R.D.I.S visual interface. T.A.R.D.I.S visual interface activated the Doctor looked at it while grabbing for the book.

He traced his finger along the page before saying "Go through your memory banks for a place named 'Central City'" When he said that, the interface replied You have not visited Central City yet he place the book down and started flicking switches turning off the interface and flicking switches.

"I've been almost everywhere at every time. How did I forget to go see the Particle Accelerator?" he asked himself, causing the T.A.R.D.I.S to hum "Oi! Don't dis the bow-tie! and secondly your the one that's supposed to remind me" he said while tapping the console.

The T.A.R.D.I.S dematerialized and materialized inside of Clara Oswald's apartment. While listening to the T.A.R.D.I.S humming, he started thinking of Clara and how much she effected his life. How much she distracts him. How much he adores her. The Doctor stopped himself from thinking more about her before he opened the door and ran out into Clara's apartment. He looked around and noticed no one was there "Clara!" he yelled before running down the hall into her room. He saw her lying on her bed with a sleep mask on. He slowly walked up to her bed and admired her features. The way her chest rises and falls in sync with her breathing. He walked closer to her and bent down so his mouth was next to her ear. "Clara..." he whispered into her ear "Clara..." he said on a hire octave. To his disappointment she didn't wake up. So when the Doctor cupped his hands around his mouth and screamed her name into her ear, she shot up and yanked off her sleep mask before falling out of bed. He climbed over the bed to look at her on the ground. "Oh good, your awake." he said as if nothing happened.

"What are you doing here?" she asked while getting up and looking at her alarm clock "At 3:47 in the morning?" she asked with her annoyed face on rubbing her temples as if she had a head ache.

The Doctor stared at her with awe at her beautiful face, now not covered by the mask. He snapped out of it when Clara walked around the bed and towards her bathroom. "I'm going back to go see Dr. Wells' particle accelerator in 2014. Wanna' join?" he asked while sitting on her bed

She yanked the door open "You came in my room and screamed in my ear just to tell me your going to some stupid particle mawachits?"

"Accelerator-" he said after she finished "Yeah, you wanna come?" he asked with a wide smile plastered on his face bouncing up and down on her bed like a 5 year old

"Sorry, but I'll have to pass. And stop jumping on my bed!" she said as she made her way back in

"Aww... Why can't you come?" he asked slouching his shoulders and making a dog face, a bad one I might add.

She looked up at him "Because I have this thing in the morning-"

"What thing?"

"It's something called a JOB" she said looking at him with a playful glare "You should go get one" she said climbing back in to bed

He stood there staring at her, dumbstruck, as if she was on fire. He stood there for several more seconds before telling her "Okay" and walking out of the room

Clara lied in bed and she didn't relies what the Doctor had said until she heard the vworping noise of the T.A.R.D.I.S coming down from the hall. She quickly got up and ran to the door way "AND KNOCK NEXT TIME BEFORE YOU COME IN MY ROOM!" she yelled at the now gone T.A.R.D.I.S. Receiving some banging on the wall from the room next to hers telling her to "SHUT UP!"

She walked to the wall and said "Sorry Mrs. Sanchez" she said as she walked back to her room

A/N: Next chapter will be about the Doctor and the Particle Accelerator. Sorry if you didn't like it.