The TARDIS lurched. Donna grabbed for the console, but by the time she was sure of her grip, they had landed.

"Set the controls to random!" the Doctor cried, gleefully. "Mystery tour. Outside that door could be any planet, anywhere, anywhen, in the whole wide...are you all right?"

"Terrified!" squeaked Donna. "I mean, history's one thing, but an alien planet?"

"I could always take you home," said the Doctor, waving a thumb over his shoulder. Donna snorted at him, and was preparing a suitable – if breathless – riposte when the door of the TARDIS crashed open and a man ran in.

They both gaped as the intruder, apparently unaware of his audience, dropped his trousers without ceremony and began struggling into a pair of blue tights. Donna coughed gently. When this failed to attract their guest's attention, she coughed more forcefully.

The newcomer looked up, readjusted his spectacles and grinned feebly.

"Sorry," he said, in a soft Midwestern accent, "wrong phone booth," and then ran for it, his exit hampered to a degree by the fact that he had his tights on the wrong way round.

"Underpants go on the inside, mate!" Donna called after him, and then felt amazingly embarrassed at having done so. She turned around to face the Doctor, who was suddenly displaying enormous amounts of interest in the ceiling.

"Was that...?" she asked, offhand.

"Yeah," he said, just as absently.

"Shall we try again?"