this kinda came to me randomly & it isn't very good but tell me what you think anyway. :D
"You cannot be serious!" Martha Jones' voice rang out from her old room as she dumped her over-night bag on her bed. "There is no such thing as a planet with trees that talk! We're not in Narnia!" The Doctor's laugh rung out around the TARDIS vibrating into every nook and cranny because he was working on the console and had accidentally hit some sort of switch that enhanced his voice.
"Where do you think C.S. Lewis got his ideas, hey?" Donna ran out into the main room excitedly waving her hands as she spoke.
"No. Way! You travelled with C.S Lewis? As in the world-famous writer?" She pulled the Doctor out by his leg and he yelped in surprise, "Does Aslan exist? Can we go see Aslan? Is he there! Martha! Let's go see Aslan!" The Doctor stood up, dusted himself off and grabbed Donna by the shoulders just as Martha came running in with a look of disbelief on her face.
"There is no such thing as Aslan. That part was his own imagination." Donna's disappointment was evident as Martha rolled her eyes and sat down on the nearby chair. "But yes Martha the trees do talk, I met a few. Ages ago, years. I was a completely different man back then." His voice softened and drifted off as he relived old memories, the two current companions knew better than to try and take him out of his trance. Martha's smile fell off her face and she felt the old familiar sting of rejection as she realised who he was thinking of.
Suddenly, the TARDIS jolted as if it collided with something and everyone was thrown upon the floor. The Doctor kept low as various objects fell from the high shelves and he crawled to Donna and Martha
"Is everyone okay?" His voice was urgent as he looked for any visible danger. Just as they were about to respond they heard a voice.
"Aww, I love this song. Turn it up!" They heard a familiar chuckle in response and a rise in the volume of the song. Martha and Donna recognized it to be Always by Bon Jovi; turning to the Doctor to ask what the Hell was going on, they found him frozen to the spot, pale as a sheet. Martha crawled over to him to check if he was okay and Donna stood up to see who their new companions were. She gasped when she looked at the pair. Slowly, as if he were a man moving underwater, the Doctor untangled his limbs and lifted himself up above the console to watch his most recent occupants; Martha's reaction wasn't any better than Donna's. His eyes grew soft as he watched the scene.
Rose was laughing and dancing around the Doctor as he used some remote control to sing to her, he couldn't keep a straight face or carry a tune. "This Romeo is bleeding, but you can't see his blood!" They laughed together as he pulled her close and spun her around and around. "I can't sing a love song the way it's meant to be." She leaned against his chest, dizzy from spinning and they sung together. "And I, will love you, baby, always!" They laughed again and resumed dancing around like idiots.
"Doctor," Donna whispered urgently, "Can they see us?" His face was broken, his eyes were filled with tears of hurt and longing, his lips were curved into a slight smile as he watched the memory.
"No," He breathed, making to hard for him to be heard over the ridiculous singing, "They're just an echo. They can't hear or see us. All we can do is watch." His eyes didn't wander from the scene as he watched himself and Rose sing to each other. Rose sung the first line whilst wiggling her hips which drew both Doctor's eyes.
"If you told me to cry for you. I could!" Then it was the Doctor's turn who was trying his hardest to look like Elvis, like he did the time they visited he 50's and she laughed as he over dramatised the line,
"If you told me to DIE for you, I would!" Then she ran to him and he tried to lift her up, the way they did in Dirty Dancing but instead of doing a perfect jump she landed on top of him, both of them laughing hysterically. Hiccupping slightly Rose sat upon his legs so as to not hurt him and began to talk.
The Doctor remembered what she was about to say and he closed his eyes. He wished upon every single star, planet and galaxy that he had ever visited in his 900 years that the next words wouldn't come out of her mouth. But he heard the syllables being formed and he knew what was happening next. He opened his eyes.
"I can't believe I get to do this forever!" The Doctor sat up with her still on his lap and draped his arms around her waist, pulling her even closer. He chuckled into her hair,
"Do what?" She sighed happily and snuggled herself into his chest, the Doctor smiled down at her,
"Be with you. Forever." For the first time, the Doctor bought Rose's lips to his. She froze at first, from the shock but the Doctor mistook it for reluctance and started to pull back. The Doctor who was watching the scene chuckled with anticipation as he remembered what happened next; Rose, sensing his withdrawal, threw herself at him to make sure he didn't escape. She managed to push them both on the floor and carried on this kiss. After a while they broke the kiss simultaneously and stood up, the Doctor took her hand and started to lead her to the corridor that carries down to his bedroom.
"Time to go." The present Doctor said, startling Donna and Martha who had been watching the scene intently, they watched Rose smile at the Doctor seductively. "TIME TO GO!" He yelled, urgently. Finally, they felt the same feeling of a collision and ended up on the floor. The memory was no longer there.
"Doctor, are you okay?" Donna asked but she didn't expect a reply. He had one tear running down his cheek.