When the Doctor sleeps, he dreams. And the TARDIS weaves herself through his dreams.
For more years than he counted, she had no physical form when he dreamed but she was there, sharing it with him, and it was a pleasant form of communion. Something to remember as he clung to her console and they rocketed through the universe together.
But things changed, as they do, and now he sees her in his dreams.
The first time was days after the Battle of Canary Wharf and he dreamed of Rose. She wore a white dress, the same she'd worn when they crashed a party at Carlton House. (Rose had attracted the Prince Regent's wandering hands, so she'd stomped on his foot and they'd run, hand-in-hand and laughing, to the safety of the TARDIS.) In his dream, she looked down at a red rose in her hands and then up at him. And her eyes were glowing with the time vortex and then she was in his arms, warm and solid and more real than she'd ever been, and when he woke, he was crying.
And he dreamed of Jack. Bombs tumbling around them and Jack's hands on his face as they kissed and the vortex in his eyes and vibrating through his fingers and this time, the Doctor woke gasping.
He walked through the TARDIS, naked, until he could rest his hands on her console. She was warm under his touch and her lights pulsed gently and he went to sleep there, curling in close to her warmth, and the grids on the floor left printed patterns on his skin.
Once, it was Reinette. Intelligent and beautiful and knowing him, understanding him, and he could smell the experience of centuries on her like perfume as they danced together in silk sheets. Only once, though.
When Martha came into the TARDIS, she came into his dreams and stayed in both.
And now, after the year that wasn't, the TARDIS has taken a new form. Slim, male, with a mocking smile and a double heartbeat. And when they're wrapped around each other, he can taste the TARDIS in the other's mouth, in his sweat, in his skin.
And he can hear the drums.