"Well, that fourth thing was harder to accomplish than I imagined," the Doctor reminisced, fiddling around with the TARDIS absentmindedly.
"'Than you imagined'? That was an iguanodon! An iguanodon!" Martha stared at him, incredulous.
He waved her off, still messing with the controls. "No, that was the lizard. Anyway, I feel like it's time for something different. Not a different planet this time. Just good old Earth." He stood up straight and bounced on his feet. "Which do you want: the past, present, or future?"
"Oh, I dunno. Past, probably."
He grinned, then strode back to the console. "Past it is, then!" He spun a dial and the whirring started up. Everything seemed to be going as perfectly normal as normal could be in a big blue box, traveling across the universe. Martha wondered how this had become the new normal for her.
All of a sudden, the console started sparking and she was pulled off her feet and sent skidding across the floor, landing in a heap against the railing. "Doctor, what's going on?"
"I don't know!" He clung onto random levers as his feet swung in the air. Once again, the floor's angle shifted, and the Doctor was thrown onto the console as Martha wrapped her arms around a pole. "I'll try to get her to land! Hang on!" He slammed his heel into a button, and the shuddering and quaking stopped.
Martha carefully unhooked her arms from the beam as he strode over to the doors and flung them open. "Here we are!"