"A time machine? Wow, that's incredible," Billy's eyes light right up, and in a second he's leaning over to study the controls intensely. They're a mystery even to him, though---he'd have to see the console in operation to even begin to understand the complexities of time travel.

After a few seconds' study, he turns back to the girl. "I can't say I've seen him. We have several Doctors, but as far as I know they're medical professionals, not time travelers."